US3782504A - Multiplex system for elevator control - Google Patents

Abstract

A system of transmitting control and indicator signals between elements of an elevator system such as between a car movable along a hatch-way and car control or supervisory equipment wherein the signals are coded and transmitted in multiplexed form over a single transmission line. A two station system between a car and a fixed location is illustrated with a transmitter and receiver at each station. The coded signals are time sequenced so that all signals are considered cyclically.

Description

United States Patent I [111 3,782,504 Billmaier et al. Jan. 1, 1974 [54] MULTIPLEX SYSTEM FOR ELEVATOR 3,203,506 8/1965 Cummins 187/29 CONTROL 4 [75] Inventors: Joseph F. Billmaier; Gordon P. j 'f" "f E 323 b th f T 1 d ssls an xammern n, Sprague o O 0 e o lo Attorney-Wilson & Fraserv [73] Assignee: Reliance Electric Company, Euclid,

Ohm 57 ABSTRACT [22] Ffled: 1972 A system of transmitting control and indicator signals 1 1 pp 314,918 between elements of an elevator system such as between a car movable along a hatch-way and car con- [52] U CL 187/29 R 340/19 trol or supervisory equipment wherein the signals are [51] Int. Cl

' 3/00 coded and transmitted in multiplexed form over a sinl gle transmission line. A two station system between a [58] Field of Search 187/29, 340/19, 21

car and a fixed location is illustrated with a transmitter [56] References Cited and receiver at each station. The coded signals are UNITED STATES PATENTS time sequenced so that all signals are considered cyclically. 3,662,861 5/1972 White et a1. 187/29 3,519,105 7/1970 Geil 187/29 34 Claims, 6 Drawing Figures i TRANSMITTER RECEIVER M 1 .E 115 i l 1 L MULTIPLEXER 1 e BIT OUTPUTS i l LAT.CH 12s l 1 1 11 52131? 1 BINARY T0 DECODER 1 I DECIMAL I24 1 DECODER 1 I 1 121 I I 122 v 17 I 1 123 LINE LINE START DRIVER I RECEIVER RiNG 11a COUNTER COUNTER l I 1 l CLOCK 1 l 116 1 1 w PATENIEH'JM 1m.

sum 1 or 4 IF-IGQI ALIMIT 'BLMIT (TRUE) E. (FALSE) SR (TRUE) (TRUE) FIG 00 (FALSE) 7 MULTIPLEXER STATION "5 TRA SMI TER RECEIVER MULTIPLEXER STATION "A TRANSMITTER RECEIVER PATENTEDJAN 1 I91 sum 3 OF 4 ABC PATENTEUJAN 11974- sum u nr 4 1 MULTIPLEX SYSTEM FOR ELEVATOR CONTROL DESCRIPTION OF THE PRIOR ART In a modern elevator system there is the requirement for communication of a large number of separate control and indicator signals between the movable elevator car and a stationary elevator controller and between various stations such as indicator panels and controls and between controllers and system supervisory controls. Heretofore, this communication has been accomplished by providing one or more cables with individual wires for each signal source to electrically link the stations such'as the traveling cable between the car and the controller. As more features are added to the elevator system these cables become progressively more heavy and costly and less flexible.

In an attempt to solve this problem the prior art has utilized the transmission of different frequencies of a single transmission line. Representative systems are disclosed in Cummins Patent entitled Radio Communication Means Between Elevator Cage and Motor Control" issued as 3,203,506 on Aug. 31, 1965 and Geil U.S. Pat. No. 3,519,105entitled Vehicle Control issued July 7, 1970. Each control signal is assigned a distinct frequency, either just a carrier or a carrier with audio modulation, which is generated by an oscillator At the receiving end of the transmission line there are filters and detectors for each signal.

Although the frequency technique eliminates the bulky flexible cable it also has the disadvantage of being complex and costly. Each control signal must have its own oscillator, filter and detector. Where there are a large number of signals involved the available frequency spectrum may dictate bandwidth .and spacing that requires the use of relatively expensive components.

SUMMARY OF THE INVENTION I Communication between components of an elevator system such as the elevator car and the elevator controller is achieved by coding binary signals and transmitt ing them along a common data line in multiplexed form. Conventional elevator control and indicator siglocal receiver has received its full multiplex signal sequence and the local transmitter has sent its full multiplex signal sequence the local transmitter is cycled to again read and transmit its multiplex signal sequence.

Signals are represented as a true or false state for each item sensed. In the example, a 32 word multiplex signal sequence is employed. A true condition for the word is signified by a short interval logic 1 and a false." condition is represented by a longer interval logic 1 Each word is made up of four bits defined by a transmitter clock such that the first and fourth bits are always a logic the second bit is always a logic 2 1 and the third bit is a logic 0 if the condition is true and 1 if the condition is'false.

The receiver section of each multiplexer is sequenced by a counter which is clocked from its opposite transmitter by each word it receives by the rising leading edge of the signal during the second bit i'nterval of the word. Decoding of the word is by means of a timer which senses the logic state of the received signal during the third bit interval of the word.

, Transitions in input conditions for a signal during that portion of a signal cycle in which that signal is being transmitted is prevented from altering the transmitted signal. A check of the input at the beginning of the signal transmission forits word sets a latch and prevents a change in the logic 1 duration dictated at the setting of the latch. Thus, changes in a condition represented by a word are indicated only during the next transmission of a multiplex signal cycle at the time signal for that word is read.

Synchronization of a transmitter. multiplex signal cycle and the inputs it reads with the receiver multiplex signal cycle and the output latches it. sets .is sensed by the completion of a local transmitter multiplex signal cycle and coincidence of completion of a local receiver multiplex signal cycle. The failure to achieve a coincidence of completed signal cycles for an excessive interval resets the transmitter to force synchronization where the transmitters of each station are arranged so they always complete their signal cycles and upon completion always enable their local receivers.

DESCRIPTION OF THE DRAWINGS 7 FIG. 4 shows a portion of a multiplex signal sequence I including several coded signals for false and trueinputs to the multiplex unit;

FIG. 5 is a schematic representation of a transmitter section which may be employed in the multiplex unit of FIGS. 2 and 3; and 1 FIG. 6 is a schematic representation of a receiver section according to the preferred embodiment of the multiplex unit of' FIGS. 2 and 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT utilized with any number of elevator cars. Elevator cars 20 and 21 are connected to one end of cables 22 and 23, while the other end of each cable is connected to counterweights 24 and 25. The cables are placed over sheaves 26 and 27 which are rotated to raise and lower the elevator cars. The sheaves are attached to the output shafts of motors 28 and 29. Generators 31 and 32 have their armatures electrically connected to the armatures of motors 28 and 29 to form a well-known Ward-Leonard system of speed control-f9) each elevator car. Each motor and generator combination receives control signals from controllers 33 and 34. These controllers determine the movement of the elevator car in response to control signals in the form of car calls, hall calls and other running signals. Where two or more elevator cars are to service the same landings, a supervisory control 35 is provided to determine, for example, the distribution of the cars and which controller will respond to a hall call.

It is apparent that there must be connections between the elevator car and its controller and the landings and the supervisor in order to transmit the necessary control signals. For example, in the five floor building shown in FIG. 1, elevator car contains a panel 36 with five pushbuttons, one for each floor, with which to register car calls. The car also includes means sensing its location alongthe hatchway such as an inductor notching switch 40 responding to the cars passing critical positions in the hatchway and controls responsive to the position of the door 50 providing a closure for its entry from the landings it serves. In'order to transmit a car call, a door control signal,or a car position signal to the controller, previous systems have utilized a travelling cable containing separate wires for each switch responsive to those factors. The present invention reduces the wires required for transmitting control signals' to a twisted pair no matter how many floors are contained in the system. The pushbuttons on panel 36 are the inputs via leads 36-1 as are door control leads 50-1 and car position leads 40-1 to multiplexer unit 37 mounted on elevator car 20. These signals are converted to coded signals and are transmitted on twisted pair 38, which may be cabled with power and telephone conductors to the car to a similar multiplexer unit 39 located near controller 33. The coded signal is decoded and sent to controller 33 which will stop the elevator car at the proper floor.

Multiplexers may also be used to send hall calls to the supervisor. Each floor except the tenninal floors has a set of up and down hall call pushbuttons 41. Thus, according to prior practice separate lines from each floor to the supervisor would be required. By utilizing amultiplexer unit, hall calls from several adjacent floors can be coded and transmitted on a twisted pair to another multiplexer unit at the supervisor. in FIG. I the top two floors have hall call pushbuttons 41 connected to multiplexer unit 42. Coded signals are transmitted on twisted pair 44 to multiplexer unit 46 where the signals are decoded and sent to supervisor 35. The first, second and third floor hall call pushbuttons 41 are connected to multiplexer unit 43 which transmits coded signals on twisted pair 45 to multiplexer unit 47.

A further example of utilizing the present invention to reduce wiring is illustrated by the indicator panel in the lobby. Indicator panel 48 has a series of lighted numbers which present a visual display of elevator car location and call registrations to persons waiting for the car. Car position signals and hall call signals from supervisor 35 are coded by multiplexer unit 49. The coded signals are transmitted on twisted pair 51 to multiplexer unit 52 where the'signals are decoded and sent to indicator 48.

In many cases it may be desired to transmit signals in both directions between two locations. In the case of elevator car 20, car location signals from controller 33 may be used to actuate a visual indicator in the car (not shown). Therefore, each multiplexer unit contains a transmitter and a receiver which are alternately activated. When the transmittor in unit 37 is sending,the receiver in unit 39 is enabled. After a predetermined period of time or the transmission of a predetermined pulse train to the receiver in unit 39, the transmitter in 39 is enabled as is the receiver of unit 37. FIG. 2 is a block diagram of a basic multiplexer unit and FIG. 3 represents a pair of coupled multiplexer stations. Transmitter section 111 and receiver section 112 are connected in parallel to data lines 113, typically a twisted pair.

The transmitter 11 1 has as inputs a start signal on line 118 and a plurality of input lines 114 which are connected to various control signal sources. As in FIG. 1 these inputs could be from the car call pushbuttons on panel 36, leveling switches as 40, door limit switches, door safety switches, manual switches for door control, and attendant-automatic service switches all on the car. When a switch is actuated, the signal is multiplexed, transmitted to the receiver section of the multiplexer unit at the elevator controller, set into the proper output to the controller, and processed by the controller.

In the case of a car call, a signal from the controller to illuminate the light of the car pushbutton for the call which is registered. is multiplexed at the controller multiplexer unit, transmitted to the receiver of the elevator car multiplexer unit and set intothe proper output for the pushbutton light. Similarly, the controller can send other signals to the car such as position indicator controls, direction, arrows, and open and close door signals. 1

As will be set forth in more detail the multiplexer transmitters 111 each include means to read the signals imposed on a plurality of inputs in a predetermined order. Normally, the read sequence for a station is re peated following the completion of a receive cycle for that station which follows the read cycle. The signals are coded as words at the initiation of their individual read intervals and are transmitted to the receiver 112 of the opposite multiplexer station over a transmission line 113. The receiver at the opposite station is sequenced by the received word signals to apply decoded individual word signals to signal storage means or latches having outputs. The sequence of application of signals to the storage means and outputs corresponds to the sequence of signal inputs read at the opposite station transmitter. Coupled to the outputs are the utilization circuits for the respective signals, which circuits can be conventional for control of the car and its signals.

The start signal on line 1 18, which may be an indication that the power has been turned on, activates a clock I16 and enables a ring counter 117. The clock, which is an oscillator running at a predetermined frequency, generates a train of pulses. Those pulses are counted by ring counter 117 which in turn produce a binary output count to binary to decimal decoder 119. The decimal count from decoder 119 steps the multiplexer so that each input signal appears at the line driver 121 in a definite time sequence. The line driver I21 transmits the multiplexed signals over data lines 113 to the receiver section of another multiplex unit. When the last coded signal has been transmitted, the clock 116 is inhibited and the receiver section 112 of the car multiplexer unit is enabled.

Inputs on input lines 114 are in the form of the presence of or absence of a voltage of a predetermined magnitude. The presence of the voltage indicates a true signal or logic 1 while the absence of the voltage indicates a false signal or logic 0. The input signals are coded in the form of a group of four pulses. As shown in FIG. 4, false is represented by a 0 pulse, two contiguous 1 pulses and another 0 pulse. A true signal is represented by a 0 pulse, a single 1" pulse and two more 0 pulses. The first and last pulses of the group serve to condition the receiver to readand time the middle two pulses which carry the information. In receiver section 112 each group of four pulses'is received by line receiver 122 and pulses advances ring counter 123 one count. The output of the ring counter is in binary form and is converted to a decimal number by binary to decimal decoder 124. The output of the decoder is utilized to sequence the 8-bit latches 125 so that information from the line receiver 122 is placed on the proper output line of a plurality of output lines 126. After the last group of pulses is read, the ring counter 123 resets the ring counter 117 of. its

multiplexer unit and the transmitter section 1 11 of that unit begins transmitting again.

A typical encoding for a simple one car system employs multiplexer units having a 32 word capacity such that the car unit, termed multiplexer unit A in FIG. 4, transmits a signal cycle of 32 words of true or false sig-' nals each of four pulse lengths in the sequence:

door open manual switch safe edge switch door protection switch I door limit, open door limit, closed leveling switch up leveling switch down notching switch up notching switch down first floor car call second floor car call third floor car call fourth floor car call any car call The receiver of the multiplexer unit at the controller, termed multiplexer unit B, is sequenced to actuate counterpart controls at thecontroller for the above signals in the order set forth. Conversely, the transmitter of multiplexer unit B has a predetermined sequence of signals for which the receiver of multiplexer unit A is correspondingly sequenced. In the example, the controller-to-car signals are sequenced for the individual car call register lights as the firstfive words, then a blank or spare word, then the five position indicator light signals for car position, then seven spare words, then door open signal, door close signal, position indicator up direction, and position indicator down direction. These signals are directed in the sequence of their receipt to actuate controls for call registration indicators, position indicators and door controls to open and close the car doors, all of which are on the car.

An initial portion of a car-to-controller signal issued by the transmitter of multiplexer unit A is illustrated in FIG. 4 wherein the first bit has a long pulse indicating the door open pushbutton, D0, in the car is not operated during that signal sequence. The safe edge switch SE signal is also represented by a long pulse indicating no safe edge operation. An obstruction in the door path operated the door protection switch, for example a safe ray (not shown) which senses interruption of a beam of radiant energy across the door path, to produce a true signal or short pulse, SR. At the moment represented, the door is partially closed since the door open limit, the A limit, is true, and it has not fully closed since the door close limit, the B limit, also is true. The remainder of the sequenced signals for the car-tocontroller transmitter cycle has not been shown.

FIGS. 5 and 6 are schematic representations of the transmitter section 111 and receiver section 112 of FIG. 2. In FIG. 5, 141 represents an inverter which converts a logic 1 at its input to a logic 0 or a logic 0 at its input to a logic 1. Element 142 is typical of a NAND gate which has a 0 output when both inputs are at 1 and a 1 output for any other combination of inputs. Element 137 illustrates the symbol for a NAND gate in negative logic.

Element 158 is typical of a NOR gate which has a 1 output when both inputs are 0 and a 0 output for any other combination of inputs. Element 161 is typical of the symbolfor a NOR gate in negative logic.

Element 169 is a NOR flip flop comprised of two NORs each with the output coupled to an input. of the other. When both inputs 1 and 2, are at 1 and both outputs, 3 and 4, are at 0. When the inputs are of opposite signals then output 3 will be at the same as input 1. If both inputs are at 0," one output will be 1 and the other will be 0 depending on which input switched to 0 first. When input 1 switches to 0 first output 3 will be 1.

Element 131 is a typical multiplexer section which has eight input lines 1 through 8, three count input lines A, Band C, and enable input 9-and an output 10. When enable 9 is at 0 the signal on output 10 is the opposite of the one selected input signal on lines 1 through 8. A combination of signals on the three count input lines selects one of the inputs to be represented at the output. For example, if all three count input lines A, B and C are at 0 then input line 1 is selected and a 0" on line 1 will produce a 1 at output 10. By providing a binary count of zero to seven in sequence at the count input lines A, B and C input lines 1 to 8 will be read in sequence.

Element 143 is a typical 4-bit binary up counter with four output lines A, B, C and D. Line 1 is a parallel enable input which when provided with-a 1" input produces a one bit count on the output lines for each 1 pulse at the input shown connected to line 129. A 0 on line 1129 enables the counter and a 1 transfers the data to the output lines. Leads 2 and 3 are a count enable which enables the counter when. they have a 1" input. Lead 4 produces a 1 only if lead 3 is a 1" and all outputs are at 1. This allows the counters to be used in series. A master reset input is connected to line 128 and a 0 will clear all the outputs.

Element 153 is a binary to decimal decoder. A 0 on input line D enables one of the four output lines 1 through 4. For example, if lines A, B and C are at 0 output line 1 will beat 0 and the other output lines will be at 1. If line A is changed to 1,'output line 2 is at 0 and all others are at 1. With inputs C and D grounded, the binary signal on lines A and B determines which output is enabled and thus which of multiplexer sections 131, 132, 133 or 134 is enabled.

Line driver 121 is utilized to transmit the coded signals of FIG. 4. Element 157 is a NAND gate and when all inputs are at 1 output 4 is at 0. A 0 on any input will produce a 1 at output 4. Output 5 is an inverting output which will have the opposite signal from line driver and is grounded through a resistor. These resistors permit the line drivers of the local and remote multiplexer to be connected to the same transmission line 113 and to function as wired ORs as independent inputs to a common output.

In FIG. 6 line receivers 122 receives the coded signals from data lines 113. Element 199 is an amplifier which produces a 1 for a.1 signal on the input and a signal on the input and a 0 for a 0 signal on the input and a 1 signal on the input.

Element 204 is an 8-bit addressable latch. A combination of signals on the inputs connected to lines 227, 228 and 229 select one of eight output lines 126. If a 0 is present on the enable input E the decoded signal from the line driver 122 will be stored on the selected output line 126 corresponding to an input line to the then effective multiplexer section and a line of the transmitter.

Element 211 is a NAND flip flop which has a l on each output when the inputs are at 0.. When the inputs have opposite signals output 3 will be the same as input 2 and output 4 will be'the same as input 1. When both inputs are at 1 one output will be at 1 and the other at 0 depending on which input switched to 1 first. When input 1 switches to 1 first output 3 will be 0.

' Element 193 is a monostable multivibrator consisting of an OR gate, a flip flop-and a timing network. The OR gate has a regular input 1 and an inverting input 2 and its output is the input to the flip flop. By placing a l on the clock input C12 the signal at the OR output will determine the Q and Q outputs for a time period determined bythe timing network of resistor 194 and capacitor 195. A 0 from the OR output produces a 0 ft O and a 1 from the OR output produces a 1 at Q.

In FIGS. 5 and 6 the terminals of various devices have been numbered or lettered and each device has a reference number. When referring to a device terminal it will be set forth as a suffix to the reference number separated therefrom by a dash, such as terminal 1 of NAND 137 in FIG. 5 designated as 137-1.

The general scheme of operation of the transmitter section 111 as shown in FIG. 5 is to sequentially consider or read each input 114 through sections 131 to 134 of the multiplexer 115 using the C and D outputs of counter section 143 and the A output of counter section 144 to enable, by binary code to the A, B and C inputs of multiplexer sections 131 to 134, a corresponding one of each of the inputs 1 to 8 of the multiplexer sections 131 to 134. Counter section 144 also individually enables the multiplexer sections 131 to 134 by binary coded signals from its B and C outputs to the A and B inputs of binary-to-decimal decoder 153. The A and B outputs of counter section 143 control the logic which generates a wide pulse for a false" state at the then effective input lead 114 and a narrow pulse for a true" state.

Counter 117 is reset when the receiver section 112 of its multiplexer station has received a full multiplex signal cycle train of signal words. This is indicated as a master reset signal on lead 147 from the receiver section ll 12. The clock 1 16 driving counter 117 is free running until inhibited by an indication of the completion of a multiplex signal cycle transmission to satisfy gate 135. When gate is satisfied it also enables the multiplexer receiver section of its multiplex station by signals on leads 173 and 174.

A multiplexer signal cycle is transmitted as thirty-two words each comprising 1 four pulse intervals of clock 116. A true word is made, up of contiguous pulses of logic 0-1-0-0 while a false word is contiguous pulses of logic 0-1-1-0. These words are transmitted to transmission line 113 from line driver 121 and are encoded by NAND 163 for a true word and NAND for a false word. Flip flop 169 is set irrevocably during the initial read portion of a word interval by the then current true or false state on the input lead 114 being read by the multiplexer 115. This enables NAND 163 and disables NAND 165 for a true signal, and enables NAND 165 and disables NAND 163 for a false signal. NAND 1563 can be gated only during the second counter pulse interval of each word interval by gating NOR 161 when counter section 143 issues a 1 on its A output and a 0 on its B output. NAND 165 can be gated only during the second and third counter pulses. During the first pulse NOR 158 receives 0 from both the A and B counter outputs and inhibits NAND 165. During the fourth pulse NAND 159 receives a 1 from both the A and B counter outputs and inhibits NAND 165. During the second and third pulses outputs A and B of counter 143 are in opposite states to enable NAND 165 from NOR 158 and NAND 159.

Flip flop 169 is set at the beginning of each word interval during the period the counter section 143 outputs A and B are both 0 as signified by NOR 158 to NOR 171 to make NOR 171 responsive 'to the signal from NAND 156 and thus the state of the effective multiplexer input 114. It is reset at the time a 1) appears from NAND 159 when both the A and B outputs of counter section 143 are at 1. Any change of the signal at input 114 to NAND 156 has no efiect after the first clock pulse interval of the word interval since NOR 171 is inhibited and cannot change the state of flip flop 169. 1

FIG. 5 is a schematic representation of transmitter section 111 of FIG. 2 for each multiplex unit. Hnputs from various control devices appear on input lines 114 in the form of a 1 or a 11". A start signal on line 118 enables ring counter 117 to receive a train of pulses from clock 116. The number of pulses counted is presented in binary form to word coder 158, 159 and 161, the reader- multiplexer sections 131, 132, 133 and 134., and the binary to decimal decoder 119. Decoder 119 enables each of the multiplexer sections 131 to 131 of 1 15 in order. As each multiplexer section is enabled the binary count enables each inputline 114 in sequence. The signals on the input lines as to an A unit are read and are coded and transmitted over date lines 113 by line driver 121 to the receiver section of another multiplex unit, the B unit. After the last input signal has been sent by the A unit, signals on lines 173 and 1'74 activate receiver sections 1 12 of its multiplexer unit, the A unit, to receive signals from the transmitter of the other multiplex unit, the B unit. When receiver section 112 of the A unit has completed receiving, it produces a signal on line 147 to enable the transmitter section 111 of its multiplexer unit, the Aunit. Lines 128 and 129 allow external resetting of all ring counter outputs and injection of clock pulses for test purposes.

The input lines 114 are separated into four groups of eight lines each which are the inputs to multiplexer sections 131, 132, 133 and 134. The particular multiplexer section is selected by the binary to decimal decoder 119 while the line is selected by a signal from the ring counter 117.

The clock 116 consists of NAND 136, NAND 137, resistor 138 and capacitor 139. During the counting cycle of ring counter 117 at least one of the inputs to NAND 135 will be until the maximum count is reached. This means that the output of NAND 135 is 1 until all inputs become 1. The output 1 is changed to 0 by inverter 141 and appears as the input at lead 137-1 of the clock 1 16. This 0 produces a l on output lead 137-3 of NAND 137 and since the input leads 136-1, 2, 3, 4 of NAND 136 are tied together, the output lead 136-5 is at 0. This output is fed back to the input of NAND 136 by resistor 138 with a time delay caused by capacitor 139.

With output lead 136-5 at 0 capacitor 139 discharges through resistor 138 since output 137-3 cannot provide enough current to keep it from doing so. Output 136-5 then changes to 1 and capacitor 139 charges up again. The cycle repeats itself providing a pulse train at a rate determined by the values of the resistor 1 38 and the capacitor 139.

The pulse train appears at input lead 142-2 of NAND 142 which in turn provides the input to the clock pulse lead of 4-bit binary up counters 143 and 144 which comprise ring counter 117. Line 118 provides a 1 on input lead 142-1 through resistor 145 and the positive power supply. If the input to line 118 is grounded, for example through an external relay, the resultant 0 signal on input lead 142-1 will cause the output 142-3 to always be 1. Therefore, the pulse train from the clock 116 will not be passed to the ring counter 117. When the ground is removed, the output will be 1 when lead 142-2 is 0 and 1) when lead 142-2 is f 1. During the time a 0 is present at the clock pulse inputs for counters 143 and 144, data can enter and it is transferred to the outputs when theclock pulse goes to 11. Leads 143-1 and 144-1 are the parallel enable inputs and when they are connected to the positive power supply as shown there will be a one bit shift in the'eounter output for each clock pulse input.

The counters 143 and144 also have a count enable which permits the clock pulse to activate the counter only if leads 2 and 3 are both at 1." On counter 143 the leads 143-2 and 143-3 are both connected to the positive power supply so counter 143 will be counting all the time. Counter 144 however has leads 144-2 and 144-3 connected to lead 143-4. Lead 143-4 is only 1 when lead 143-3 is 1 and all output leads A, B, C and D are 1. Therefore, counter 144 will not count until counter 143 has registered 15 counts. The next count changes the front output of counter 144 to 1 and sets all the outputs of counter 143 to 0. This puts a 0 on lead 143-4 and counter 144 will not register another count until counter 143 has registered 15 more counts. When l27 pulses have been registered all the counter outputs will be at 1 and the output NAND 135 will change from 1" to 0. The input 137-1 will be 1 and the 1 from output 136-5 is the input to 137-2 producing a 0 at 137-3 and stopping the clock. The

clock will only start when the ring counter117 is reset. Line 118 is also connected to input lead 146-1 of NAND 146 which provides the master reset signal to the counters 143 and 144. A 0 at the master reset clears all the outputs of the counters. Again, if line 118 is grounded NAND 146 can only provide a 1 so the removal of the ground enables NAND 146. The signal to reset the counters is applied to line 147 from the receiver section 112 as a 0 and is changed to a 1 by inverter 148. Now input leads 146-1 and 146-2 both are at 1 which produces a 0 output on lead 146-3 to reset the counters. This reset occurs when the receiver section 112 has completed receiving its data and the transmitter section 1 1 1 is ready to begin a transmission.

Lines 149, 151 and 152 are the 4, 3 and 16" count outputs from the counters 143 and 1. These outputs are used to control the selection of input lines 114, eight of which go to each multiplexer section. Using multiplexer section 131 as representative of the four shown, it has inputs 131-1 through 131-8, enable input 131-9 and output 131-10. When the enable input 131-9 is at 0 the output 131-10 represents the inverse of the input signal on the lead 114 selected for reading by the combination of signals on output lines 149, 151 and 152. For example, when the output lines 153-1 to 153-4 are all at 0, output 131-111 is 1 if the input line 114 selected is 0."

' The ring counter 117 changes output when a 1 from 142-3 or 129 appears at the clock pulse input. Since the output of clock 116 is 1 when the ring counter is reset the ring counter will not record a count until the second 1 is produced by the clock. Therefore, during the four pulses of each word interval as the counter goes from binary zero to a binary three lines 149, 151 and 152 remain at 11. This combination of inputs to the A, B and C terminals of the multiplexer sections selects the first input line for each multiplexer section. During the next four pulses line 149 and the A inputs are 1 and the second line in each multiplexer section is selected for reading. As the ring counter progresses, each input line is selected in turn and is held for four counts until 32 word intervals have been generated. Therefore, during'the 128 clock pulses required for one cycle of the ring counter, the input lines can be selected four times. However, each multiplexer section has an enable input that receives signals from a binary to decimal decoder 153. The sequencing of the decoder limits each line to one reading during a ring counter cycle.

The 32" and 64 count outputs from the ring counter are inputs 153-A and 153-B. inputs 153-C and 153-D of the decoder are tied to ground so that a 0" is present. During the first thirty-two pulses all the inputs to decoder 153 are at 11 which puts a 0 on enable input 131-9 and a 1 on all the others. Therefore, multiplexer section 131 reads all of its input lines in order. During the next 32 counts, input 153-A is at 1 while the others remain at 1 1 which puts a 0" on enable input 132-9 and a 1 on all the other enable inputs. After 128 pulses all four multiplexer sections have read each of their eight input lines one time.

The outputs of the multiplexer sections are the inputs to NAND 156. As long as one of the inputs is 11 the output is held at 1 and it only goes to 0" when all inputs are 1. Since the output of a multiplexer section is 1 when it is not enabled three of the inputs to NAND 156 will always be 1. The fourth input will be the output of the multiplexer section that is enabled which is the inverse of the input line 1 14 that is selected for reading at that moment. Therefore, if during the first four clock pulses input line 131-1 is at 1, output 1131- will be at 0 making the output of NAND 156 1. Thus the signal on the selected one of input lines 114 will appear at the output of NAND 156.

The line driver 121 has three inputs which are connected to NAND 157. input 157-3 receives the output from NAND 135 which is 0 only after the last pulse in the ring counter cycle thus the line driver is enabled during a transmission cycle and inhibited upon termination of that cycle until the next transmission cycle. The other two inputs receive signals from the signal word encoding or defining logic network which combines the output signal from NAND 156 and the word defining 1 and 2 count outputs from the ring counter. The 1 and 2 count outputs are the inputs to NOR 158, NAND 159 and NOR 161. Before the first pulse in the ring counter cycle, all ring counter outputs are at 1. A reset pulse on line 147 at the beginning of a transmission resets the ring counter outputs to 0. This is the zero pulse interval which puts leads 158-1, 158-2, 159-1, 159-2, 161-1 at 0 and lead 161-2 at 1 since the 0 is changed by inverter 162.

Each word interval of four counts is defined by a first clock interval in which the A and B outputs of counter 143 are logic 0, a second interval in which A is at 1 and B is at 0, a third interval in which A is at 0 and B is at 1 and a fourth interval in which A and B are both 1. Thus the first word in a transmitted signal sequence is encoded during binary count zero through three, the second word during binary count four through seven, the third word is encoded during binary count eight through eleven, etc.

are l. Inverter 168 makes 169-1 0 so that the set flip flop is enabled for transfer of state if a 1 is applied at 169-2. inverter 164 makes 171-2 0 so that NOR 171 is responsive to invert the signal from NAND 156 and the active input 114. if during the initial pulse interval NAND 156 issues a 1 for a true signal, 169-2 remains 0 and the latch holds 169-4 1 and 169-3 0. If NAND 156 issues a 0 for a false signal 171-3 and 169-2 transfer to a 1 and the latch changes 169-4 to 0 and 169-3 to 1.

During the second and third pulse intervals of the word encoding period NOR 158 is inhibited by a 1 on lead 158-2 and 158-1 respectively, so that 158-3 The initial logic 0 of each encoded wordis developed on the non-inverting output, the Aline of the transmission line 113, by coincident l s to the input of NAND 157. With 143 -A and 143-8 both 0, the 1 and 0 input to NOR 161 produces a 0 output on lead 161-3 which is the input lead 163-2 of NAND 163. The 0 at NAND 163 makes output lead 163-3 go to 1 which is the input at lead 157-2 of the line driver. The 0 inputs to NOR 158 produce a 1 output which is changed to a .0 by inverter 164 and is the input for lead 165-1 of NAND 165. This produces a 1 output at 165-4 which is input 157-1. Therefore, all inputs to the line driver are a 1 producing a 1 from inverting output 157-5 to lead 113-8 and a 0 from output 157-4 through amplifiers 167 and 166 thereby transmitting a 0 on data line 113-A.

In order to avoid transmission of signal transistions which occur during the transmission of a word, transmitter 1 1 is provided with a latch for the signal from the active input lead 114 which is set during the initial clock pulse interval of each word is maintained through the second and third pulses, and is reset in the fourth clock pulse interval of that word. Flip flop 169 provides that latch by being set to issue a 1 at 169-4 and a 0 at 169-3 for a true input at the lead 114 being read and being set to issue a 1 at 169-3 and a "0" at 169-4 for a false input.

In the set state flip flop 169 has 169-1 at 1 and 169-2 at 6" so that 169-3 is 0 and 169-4 is 1. The initial pulse interval of each word imposes 0" on 158-1, 158-2, 159-1 and 159-2 so that 158-3 and 159-3 holds a 0 to hold 171-2 1" to hold 169-2 0 in the face of any change on 17 1-1. Thus flip flop 169 retains the state established during the initial interval over the second and third intervals.

Reset of the flip flop during the fourth pulse interval of each word encoding period is accomplished through NAND 159 and inverter 168. At the time 143-A and 143-13 are 1", 159-3 is 0 and 169-1 is 1".158-3 is 0 so that 171-2 is1and 171-3 to 169-2 is 0.This

insures 169-3 is 0 and 169-4 is 1.

Assuming that input line 114 to 131-1 has a 0 input, the output of NAND 156 will be 0 during the time the ring counter counts the zero" pulse interval of the word cycle. The 0 output from inverter 164 to input 171-2 enables NOR 171 and the 0 on input 171-1 produces a 1 at output 171-3. When the one pulse interval is counted, input 158-2 becomes 1 changing outputs 158-3 to 0 and changing input 171-2 to l. The 1 on input 171-2 will produce a 0 at output 171-3. The change of state of output 171-3 is delayed by capacitor 172. Therefore, the input signal on input line 1314 sets flip flop 169 during the one pulse interval. Any change in the input signal on line 131-1 after the one pulse interval is counted will not be transmitted until the next transmission cycle of transmitter section 111 is initiated.

The one pulse interval also changes input -1 to 1. Although input 159-2 changes to 1, the output 159-3 remains, at 1 which is the input at 165-2f. This 1 is changed to 0 by inverter 168 which supplies the signal to lead 169-1 of flip flop 169. The 1 output from 171-3 changes to 0, but is delayed by capacitor 172. With a ti on lead 169-1 and a1 on lead 169-2, output lead 1159-33 is at 1 and lead 169-4 is at 0. The change on lead 169-2 does not produce a change in either output of flip flop 169.

The 1 on lead 169-3 is'the input on lead165-3 making all inputs to 165 1 and the output 165-4 a 0". This produces a 0 on output 157-5 and a 1 on output 1574. Therefore, at pulse two a. 1 pulse 1 appears on data line 113-A.

At pulse three the input leads to NOR 1 58, NAND 159 and NOR 161 reverse polarity which does not change their outputs and consequentlythe 1 pulse remains on data lines 113 during the binary two count. On pulse four both inputs to NAND 159 are at 1 so output lead 159-3 become 0" changing the output of NAND 165 to 1. Inputs 157-2 and 157-3 remain at 1" so the output lead 157-5 changes to 1 and output lead 157-4 changes to 0 putting a 0" on data lines 113. During the four count period, pulses one through four, the data lines were 0 for pulse one, 1" for two pulses, and"0" for the last pulse'producing a signal representing a 0" on the'input line.

The on output lead 159-3 during the fourth pulse interval is changed to a 1 by inverter 168. The l and 0 inputs to 169-1 and 169-2 produce a change of state in flip flop 169 whereby output lead 169-3 is at 0 and output lead 169-4 is at 0. This is the reset of flip flop 169. v

On pulse five (binary count four) input line 114 at terminal 131-2 is selected. Assuming a 1 signal is present, the output of NAND 156 is 1 which is the input to NOR 171. During pulses five to eight the inputs to NOR 158,NAND 159 and NOR 161, will change as was detailed above. The outputs of flip flop 69 will remain at 0 for 169-3 and at 1 for 169-4. However, at pulse. six (the second pulse interval of this word and binary count five) when input lead 163-2 is in 1 the input lead 163-1 is also 1 producing a 0 output at lead 163-3 whichchanges output lead 157-5 to 0 and output lead 157-4 to 1. On pulse seven lead 163-2 changes back to .0, output lead 163-3 goes to 1 and the outputs of NAND 157 switch placinga 0 on data lines 113 which remains there during pulse eight. Therefore, during the four count word encoding period, pulses tive through eight, the data lines were 0 for one count, 1 for one count and the 0 for two counts producing a signal representing a 1 on the input line and the ring counter has a binary seven output.

FIG. 6 is a schematic representation of the receiver section 112. Coded signals from a transmitter section are received on data lines 113 by line receiver 122. Ring counter 123 produces a binary count which is utilized by binary .to decimal decoder 124 to select 8- bit latch sections 204, 205, 206 and 207 of latch 125 in order. The binary count also enables each output line of latch 125 in sequence corresponding to the reading sequence of inputs 114 at the opposite'station so'that the coded signals are stored on the output lines 126 as the same signals on input lines 114.

Each word transmitted to the line receivers 122 clocks the ring counter 123 to selectively enable the latches or signal storage means and establish the decoded signal on its individual output terminal 126. Decoding is accomplished by time synchronism of the state of the word signal as high or low during the third pulse interval defined by the clock 116 of the transmitter 111 from which signals are being received. A timer enables the latches 204, 205, 206 and 207 by means of a signal imposed on the enable input E from gates 222, 223, 224 and 225 which are gated only during the third pulse interval of each word. This selective gating is accomplished by a timer 212 defining an interval greater than one pulse interval'and less than two pulse intervals of the transmitter clock 116 of the remote multiplex transmitter. Such interval is initiated on the rising signal of the second pulse interval of the word so that it expires during the third pulse interval. When it expires it issues a clocking signal to counter 123 and an enabling signal to the latches to permit the active latch to respond to the then high or low signal representing respectively a false or true signal as decoded. Thus counter 123 is responsive to thirty-two steps in each cycle as imposed bythe thirty-two word intervals of a multiplex signal sequence from the transmitter.

Receiver 112 of FIG. 6 responds to a train of words transmitted from a remote station transmitter corresponding to transmitter section 111 of the multiplexer unit discussedahove. When the transmitter section 1 l1 of the local station has transmitted a full multiplex signal cycle train of signal words, a master reset signal on line 174 resets the counter sections 183 and 184. Each word of the signal cycle being received begins with a 0 pulse which produces a 1 from NAND 203. The 1 sets flip flop 211, which in turn resets monostable multivibrator 212. Monostable multivibrator 212 is then set by the second pulse of each word which is always a 1 and a timing interval one and one-half of the pulse interval of the transmitter clock 1 16 of the remote station is produced. At the end of the timing interval, the Q output returns to 0 which enables NAND gates 222 to 225. The-D output of counter section'183 and the A output of counter section 184 enable, by binary code to the A and B inputs of binary to decimal decoder 231, the latch sections 204 to 207. The A, B and C outputs of counter section 183 enable, by binary code on lines 227, 228 and 229,a corresponding one of each of the outputs 1 to 8 of the latch sections 204 to 207. The signal applied to the selected output is that present during the third transmitter clock pulse interval of each word from lines 113 as indicated by NAND 203.

Completion of the reception of a multiplexer signal cycle gates NAND 185 to inhibit further reception of signals in latch by changing the state of NAND 203 and through NAND 192 resets failure timer 193 while gating NOR 186. This indicates reception is complete to reset the local multiplexer transmitter section 1 11 on line 147.

While normal operation involves the alternate advance of a local transmitter 111 through its predetermined order of reading functions to send a multiplexed signal sequence to the remote receiver to which it is coupled by transmission line 133, followed immediately by a signal reception sequence by the local receiver 112 from the remote transmitter,it is possible, particularly during start up of the system,that the transmitter is out of synchronism with the receiver to which it is sending signals. Such absence of synchronism causes the system to lockup since the failure to produce a coincidence of an indication of a completed local transmission utilizing one hundred twenty-eight pulses through gate of P16. 5 and the indication .of completion of local reception of 32 word periods through gate 135 of FIG. 6 fails to gate NOR 136 to issue a transmitter reset signal on lead 147. in case of a failure to reset a resynchronizing sequence is provided.

Resynchronization is instituted by failure timer 193 which initiates a timing interval at the beginning of a receiving sequence and is reset upon completion of the receiving sequence. 1f timer 193 is not reset it ultimately times out and starts a new transmission sequence. in general, the two station multiplex system of this invention employs like transmitters and receivers at each station. However, in the case of a failure timer only one timer is required. Hence, the failure controls 200 within the dashed boundries of FIG. 6 need be included in only one receiver, as at the controller station 39, and the car top station 37 can be considered to have each of switches 235, 236 and 237 open and each of switches 238 and 239 transferred from their illustrated position to the alternative position to couple inverter 188 directly to reset lead 147 through lead 240.

When all the output lines on ring counter 117 of transmitter section 111 are at 1, the output of NAND 135 ischanged from 1 to 0 which is inverted to a 1 on lead 174 by inverter 141 and is again inverted to a 0 by inverter 182 and resets counter 123 of the local receiver. The switch in signals on line 173 produces a 1 from inverter 141 on line 174. Capacitor 181 passes a short 1 pulse which is converted to a 0 pulse by inverter 182. This 0 pulse is transmitted to the master reset input of the 4-bit binary up counters 183 and 184 comprising ring counter 123. The ring counter is reset with all outputs becoming 0. The outputs of the ring counter are also inputs to NAND 185 which produces a 1. That 1 initiates failure timer 193 timing interval as will be described. If the counter 123 reaches a count of thirty-two within the interval of timer 193, completion of a signal reception sequence is indicated by transfer to a 0 from NAND 185 to NAND 192 to reset timer 193 and the application of a 0 to NOR 186 at 186-1 which causes a reset of the transmitter counter to begin anew transmission sequence. Lead 186-2 has a 0 signal from line 173 as its input producing 0 output until 186-1 goes 0. Since line 186-1 has been at 1 a 0 on output lead 186-3 had no resetting effect until 181-1 changing .0 made 181-3 1." This signal shift makes capacitor 187 and the inputs to NAND 188 1. The output of NAND 188 is 0. If failure circuit 200 is disconnected, the 0 is applied directly to lead 147 as a reset signal. With failure circuit effective the 0 is changed to 1 by inverter 189 and is the input to lead 191-2 of NOR 191 to develop a 0 at output 191-3 which-resets the counters in the transmitter section 111 through line 147.

I The 1 from NAND 185 is also present at input I 192-2 of NAND 192. The other input 192-1 is connected to line 174 and carries the inverse of the signal on line 173, a 1. The 1 inputs produce a 0 output at 192-3 which is applied to the inverting input 193-2 of monostable multivibrator 193.

While the 0" is imposed on 193-2 timer 193 times an interval determined by the time constant of the resistor 194 and capacitor 195, chosen to be excess of a multiplex signal sequence interval from the transmitter 111. If a full signal sequence is received to transfer 192-2 to 0, the l at 193-2 enables input 193-1 to becomeeffective as a reset for failure timer 193. lnput 193-1 is connected to a clock formed from resistor 196,

capacitor 197 and NAND 198 which generates a pulse train at a frequency greater than the timing period of monostable multivibrator 193 that resets the multivibrator to prevent it from timing out.

The 1 on line 174 also enables the line receiver 122 to generate pulses which correspond to those transmitted on data lines 1 13 from the remote transmitter 111. A 1 from amplifier 199 on input 201-2 of NAND 201 and the 1 on input 201-1 produces a 0 as the input to inverter 202. Therefore, the output of the inverter is the same as the input to the line receiver 122 at non-inverting lead 113-A. The 1 from NAND 185 indicating the reception sequence is incomplete enables NAND 203 so that its output corresponds to the output of the line receiver. The four pulse false signal word on data line 113 which consisted of a 0" pulse, two 1 pulses and a 0 pulse is now a 1" pulse, two 0 pulses and a 1" pulse at output 203-3. This signal is the to the 8-bit addressable latch sections 204, 205, 206 and 207.

Using the false signal as an example, the first 1 pulse is changed to a 0" by inverter 208 and is the input at 209-1 of NAND 209. This produces a 1" at input .211-1 of NAND flip flop 211. Output lead 211-4 will be at 1 if input lead 21 1-2 is at 0 or it will not have changed from its previous state if 211-2 is at 1. Assuming for the moment that input 211-2 is at 1 and the previous state of output 211-4 was 1, monostable multivibrator 212 has a pulse train at input 212-2 of a frequency which prevents it from timing out and keeps the Q output at 1. This 1 is the input to inverters 213 and 214 which produce a 0 output from NAND 215. NAND 216 has all its inputs tied together so there is a 0 at input 217-2 of NAND 217. This produces a 1 at input 211-2 which supports the first part of the above assumption.

Pulse two from NAND 203 is a 0 which is changed to a 1 by inverter 208 placing a 1 on both inputs to NAND 209. The output of NAND 209 changes to 0. Input 211-2 remains at 1 so output 211-4 becomes 0. This 0" at inverting input 212-1 starts the timing of the multivibrator 212 which is completed in the middle of the third pulse. At that time the Q output switches from 1 to 0. This 0 is applied at 218-1 of NOR 218. The output of NOR 218 is 0 unless both inputs are 0. The 0 is changed to a 1 by inverter 219 but is delayed by capacitor 21 so that momentarily both inputs are 0 and a 1 pulse results. This pulse enables NAND 222, 223, 224 and 225 so that the correct latch is addressed and the third pulse is read.

If the signal is high on line 113-A during the third pulse interval of the word currently being transmitted, the signal 203-3 to the latches 204 to 207 is low and conversely if it is low at 113-A the signal to the latches is high at 203-3. The latches store the signal so that the memory and its output 126 addressed at the moment is set in a low state representing the false signal at the then active transmitter input 114 or in a high state representing the true state at active input 114 if that be the case. Thus, as shown in FIG. 4 if the door open signal D0 is the transmitted word and is false",the high during the third pulse interval results in a low on the DO output 126, which is 204-1 in the example. Similarly, a true safe ray signal SR has a low' third pulse interval for its word as shown in FIG. 4 and would cause its output lead 126, 204-3, to be high.

The change of output Qof 212 to a 0 also is applied to inverters 213 and 214. Capacitor 226 provides a delay. After the delay, both inputs of NAND 215-are 1 and produce a 0 causing the output of NAND 216 to change to 1. This 1 provides the clock pulse on lead to counters 183 and 1 of ring counter 123.. initially outputs A, B, C and D of 183 and A of 184 are all 0. The first clock pulse on 180 produces a binary 1 count as a 1 on output 183-A and lead 227, while leads 228, the 2 lead, and 229, the 4 lead, remain at 0. These leads provide the address to the latch sections. The 1 on lead 227 is delayed until after the third pulse is read and stored at output 204-1 while the address lines are at 0. The delay is provided by capacitor 220 which prevents NAND 216 from changing state for apredeterrnined time. When the delay is over lead 227 goes to 1" and output line 204-2 is selected for storage of the second bit of information. Thus, the latch is addressed prior to being enabled from gate 222, 223, 224 or 225 and for subsequent words inthe multiplex signal sequence that address is established during the terminal portion of the preceding word period.

The 8 and 16 count outputs from the ring counter 123 are inputs 231-A and 231-B of binary to decimal decoder 231. inputs 231-C and 231-D are tied to ground so that they are always 0. During the first eight pulses all the inputs to decoder 231 are at and the zero count output puts a 0 on inverter 234 to produce a 1 at input 222-1 of NAND 222. All other count outputs of decoder 231 are at 1 thereby inhibiting gates 223, 224 and 225. Since NAND 222 is enabled by a 1 on input 222-2 a 0 is applied to the E input of 2114 which enables latch section 204. As a result, the 0 which was the third pulse from the transmitter is placed on the first output line of latch 204. In this way the latches are set in the same order as the input signals on.lines 114 were processed by the transmitter.

The fourth andlast pulse in the group comprising the signal word in the multiplex signal cycle is a 0 which is a 1 at 203-3. This 1 is changed to a 0 by inverter 208 which produces a 1" output from NAND 209. Since the Q output of multivibrator'212 is still 0, input 217-2 remains at 1 and, with the 1 on input 217-1, produces a 0 on output'217-3. The 1" and 0 inputs to NAND flip flop 211 change output 211-4 to 1. This allows the pulse train at input 212-2 to change the Q output to 1 where it will remain until changed by the next group of four pulses.

The 1 at Q of 212 for the reset timer is .the input to inverters 213 and 214 and produces a 0 at input 215-1 changing the output to 1. The output of NAND 216 becomes 1) which produces a 1 from NAND 217 holding NAND flip flop 211 with a 1" at output 211-4 which supports the second part of the previous assumption.

The next group of four pulses will advance ring counter 123 and the information will be stored on the second output line of latch section 204. When the last group of four pulses is received all the outputs of the ring counter will be ,1 changing the output of NAND 185 to 0 and producing a 0" on line 147 through NOR 186 inverters 188 and 189 and NOR 191 to reset the local multiplexer transmitter and start its clock. Failure timer 193 is reset by the 0" at 192-2 to issue a resetting 1" to 193-2 so that 6 remains 0 to 191-1. If the receiver fails to respond to its full multiplexer signal sequence by failing to advance its counter 123 through a count of thirty-two, NAND gate185 would not besatisfied and would continue to issue a 1 to NAND 192 at 192-2. This would maintain 192 gated and continue the timing of timer 193. At the end of the timer interval output 6 of timer 193 would shift to 1" causing NOR 191 to issue a 0 at 191-3 to lead 147 thereby restarting the local transmitter.

Synchronization of the transmitter of each station with the receiver of its opposite station is normally maintained by starting transmission from transmitter A to receiver B simultaneously with the start of reception by receiver B. At the end of transmitter As transmission it starts receiver A by resetting counter 123, enabling line receiver .122, starting timer 193 through NAND 192 and enabling its reset NOR 186. If at that time receiver B has completed its reception it gates its NOR 186 to start transmitter B by resetting its counter 117 to enable its line driver 121 and clock 1 16. This alv temate transmission andreception at each station continues if the termination of transmission from one station coincides with the termination of reception by the other.

At times the transmission and reception can be out of synchronization. That is a door open signal DO might be sent as a first word and received as a safe edge signal SE, the second word of the multiplex signal cycle. Such loss of synchronization is corrected by the interlocks which start local reception when a full word count of local transmission is completed and which prevent local transmission until a full word count of local reception or until expiration of a delay sufficient to assure that the remote station transmission has been completed. This delay may be several times a normal multiplex signal sequence cycle, the thirty-two words in the example.

Assume for illustration that on starting the system both transmitters begin to transmit andthat multiplexer 39 (the unit having failure timer 193) is ahead of the other unit, unit 37. When 39 completes transmission it starts its receiver which receives the residue of the signal from 37. Receiver 39 continues to receive as transmitter 37 completes its transmission. Receiver 37 is set to receive but transmitter 39 is not transmitting. Since transmitter 37 has stopped transmitting and receiver 39 received only the terminal portion of its transmission the system is stalled. Timer 193 times out and starts 39 transmitting. At this time receiver 37 has been conditioned to receive and, therefore, starts receiving in synchronism with transmitter 39. Thereafter, synchronism is maintained since transmitter 39 and receiver 37 complete their cycles simultaneously and start their receiver and transmitter respectively at the same time.

As another illustration,assume that both receivers started partially through a receiving cycle. Neither transmitter would transmit and timer 193 would time out in due course. Transmitter 39 would be started and would fill receiver 37 so that as transmitter 39 continued transmitting, transmitter 37 would start. We thus would have the conditions first mentioned and that sequence of events would proceed until a second timing out of failure timer 193 would place the stations in synchronism.

Other conditions which might exist where the stations were out of synchronism include both transmitting with transmitter 37 ahead of transmitter 39; transmitter 39 ahead of receiver 37; transmitter 39 behind receiver 37; receiver 39 ahead of transmitter 37; and

receiver 39 behind transmitter 37. In each instancethe sequences run to a time out of the failure timer and then run through the preceding sequences to achieve synchronization.

In order to be compatible with existing elevator circuitry it may be necessary to provide a buffer consisting of a voltage divider and capacitor for each input line 114 to reduce the input voltage from the signal applying switch associated therewith. Also, each output line 126 may require a driver to raise the output voltage to a level compatible with the circuits to be controlled by the output signal. These are well-known techniques and do not form part of the invention.

While specific circuit arrangements have been employed to illustrate this invention, it is to be appreciated that other circuits are within the skill of the art for achieving the functions and interrelationships of this invention. For example, the high and low signals transmitted could be high frequency and low frequency signal bursts sequenced in the manner disclosed and be decoded by high and low pass filters. Accordingly, the above disclosure is to be read as illustrative and not in a limiting sense.

What is claimed is:

l. A control system for an elevator including an elevator car, a controller for said car, and drive means for driving said car between a plurality of landings served thereby comprising a first station having elevator controls; a second station having elevator controls; a transmission line coupling said first station and said second station; a plurality of signal inputs at said first station; means to read said inputs individually in a predetermined order; a'transmitter at said first station coupled to said transmission line for transmitting signals from said reading means in the order said signals are read; a receiver coupled to said transmission line at said second station; a plurality of signal storage means at said second station; means to couple signals from said transmission line individually to individual signal storage means in a predetermined order corresponding to the order said signal inputs are read by said reading means, said storage means corresponding to said signal inputs; and signal outputs at said second station from said signal storage means.

2.. A control system according to claim It wherein said first station is on said elevator and said second station is associated with the controller remote from said elevator car; means on said car responsive to car position coupled to one of said signal inputs to apply a signal thereto; and coupling means to said drive means from said signal output of said second station for said storage means corresponding to said car position responsive signal input.

3. A control system according to claim 1 wherein said car includes an entry; a closure for said entry; means sensing the position of said closure in said entry and applying signals responsive thereto to one of said signal inputs; and coupling means to said controller forsaid car from said signal output at said second station corresponding to said closure position responsive signal input.

4. A control system according to claim 1 wherein said car includes an entry; a closure for said entry; controls for said closure for applying signals to one of said signal inputs; and coupling means to said controller for said car from said signal output at said second station corresponding to said closure control signal input.

5. A control system according to claim ll wherein said car includes means for registering car calls for service to the landings by passengers within said car for applying signals to said signal inputs; and coupling means to said controller for said car from said signal outputs at said second station corresponding to said car call signal inputs.

6. A control system according to claim 1 including a plurality of means for generating different car operating signals mounted on said car, means coupling each of a plurality of said signal generating means to respective ones of said signal inputs as said first station; and coupling means to said controller for said car from said signal outputs at said second station corresponding to said signal inputs for said car operating signals.

7. A control system according to claim 6 including a traveling cable extending between said car and a fixed location in structure severed by the car wherein said first station is on said elevator car and said transmission line is incorporated in said traveling cable.

8. A control system according to claim 1 including, means to sense the completion of the reading of predetermined inputs; and means to enable a repetition of the reading of said inputs individually in said predetermined order in response to said completion sensing means.

9. A control system according to claim 1 including encoding means to encode signals read by said signal reading means for transmission by said transmission line; and decoding means to decode encoded signals received by said receiver to a form for application to said signal storage means.

10. A control system according to claim 9 wherein said encoding and decoding means are for binary sig' nals.

11. A control system according to claim ll including a plurality of signal inputs at said second station; means to read said inputs at said second station individually in a predetermined order; a transmitter at said second station coupled to said transmission line for transmitting signals from said reading means at said second station in the order said signals are read; a receiver coupled to said transmission line at said first station; a plurality of signal storage means at said first station; means at said first station to couple signals from said transmission line individually to individual signal storage means at said first station in a predetermined order as received by said receiver at said first station; signal outputs at said first station from said signal storage means at said first station; means for enabling said transmitter at said first station while inhibiting said receiver at said first station; and means for enabling said transmitter at said second station while inhibiting said receiver at said second station.

12. A control system according to claim till including means for enabling said receiver at said first station while inhibiting said transmitter at said first station; and means for enabling said receiver at said second station while inhibiting said transmitter at said second station.

13. A control system for an elevator comprising a first station and a second station; transmission line means coupling said first station and said second station; a transmitter at each station adapted to generate a regular cyclic sequence of signals for discrete elevator operating functions; a receiver at each station adapted to receive a sequence of signals for discrete elevator operating functions corresponding to the sequence and functions of the signals generated by said transmitter of the station coupled thereto by said transmission line; and means to maintain each received signal for said receivers until said signal is altered during a regular cyclic sequence of signals from the transmitter from which it was received.

14. A control system according to claim 13 including a plurality of signal sources at each station for said signals for discrete elevator operating functions; signal encoding means at each station for encoding signalsirom said respective sources for said respective transmitters; and signal decoding means at each station for decoding signals received by said respective receivers for application to said signal maintaining means.

15. A control system according to claim Ml including scanning means for said transmitter at each station for scanning said sources at said station; signal latchmeans for said transmitter actuated during an initial portion of the scan of each source by said scanning means to latch the currently scanned signal; and means enabling said encoding means during a portion of the scan of each source by said scanning means which is subsequent to said initial portion to encode the latched signal.

16. A control system according to claim 13 wherein said transmitter at said each station and said receiving means at said station are connected in parallel to said transmission line means.

17. A control system according to claim 16 including means to inhibit reception by the receiver at each station during transmission of signals by said transmitter at said station.

18. A control system according to claim 16 including means to enable reception by the receiver at each station upon completion of each transmission of a cyclic sequence of signals by said transmitter at said station.

19. A control system according to claim 13 including a plurality of sources of discrete elevator operating signals at each station; said transmitter at each station including means for scanning the sources at said station in a predetermined sequence; means at each station for encoding each signal as it is scanned; said receiver at each station including means for scanning said signal maintaining means in synchronism with said scanning means of said transmitter at the opposite station; and means at each station for decoding each signal received by said receiver.

20. A control system according to claim 19 including means to generate clocking signals, said clocking signals actuating said source scanning means; and means actuating said encoder in response to said clocking signals and in synchronism with the scan of individual signal sources.

21. A control system according to claim 19 including means to define a signal characteristic of each encoded signal; and means for actuating said signal maintaining scanning means in response to said defined signal.

22. A control system according to claim 19 including means todefine a signal characteristic of each encoded signal; and means for actuating said decoding means in response to said defined signal.

23. A control system according to claim 19 including means associated with the transmitter at each station to generate clocking signals; means 'to advance said source scanning means in response to said clocking signals; means to actuate said encoder in response to said clocking signals and in synchronism with the scan of individual sources; means to produce a signal characteristic of an encoded signal for each encoded signal; means associated with the receiver at each station to advance said signal maintaining scanning means in response to said characteristic signal from the transmitter at the opposite station; and means for actuating said decoding means in synchronism with the advance of said receiver associated scanning means in response to said characteristic signal.

24. A control system according to claim 13 including individual sequencing controls for said first and second stations for mutually exclusive enabling of said transmitter and receiver of each station.

25. A control system according to claim 13 including means to sense an absence of synchronism in the sequence of signals transmitted by the transmitter at one of said stations and the signals received by the receiver at the station opposite said one station.

26. A control system according to claim 13 including means at each station for said transmitter at said station for sensing the completion of a cyclic sequence of signals generated by said transmitter; means at each station for said receiver at said station for enabling said receiver at said station in response to completion of a cyclic sequence of signals generated by said transmitter at said station; means at each station for said receiver at said station for sensing the completion of reception by said receiver of a predetermined number of signals generated by said transmitter at said opposite station; and means at each station to recycle said sequence of signals generated by said transmitter for said station in response to the completion of reception by said receiver at said station of said predetermined number of signals.

27. A control system according to claim 26 including a timer defining an interval initiated upon enabling a receiver at a station and of a length exceeding the time required to complete reception by said receiver of said predetermined number of signals; and means responsive to expiration of said interval without completion of reception of said predetermined number of signals to recycle said sequence of signals generated by said transmitter for said station.

28. In an elevator system including an elevator car movable in a hatchway, a source of a plurality of first control signals in said car, a control unit responsive to each of a plurality of second control signalsin said car;

a prime mover, a fixed controller for controlling said prime mover in response to each of said plurality of first control signals, a source for said plurality of second control signals in said controller and a communication system for sending said pluralities of first and sec ond control signals in multiplexed coded binary form between said car and said controller, said communication system comprising a first transmitting means for said coded first control signals, a second transmitting means for said coded second control signals, a first receiving means responsive to each of, said coded first control signals, a second receiving means responsive to each of said coded second control signals and connecting means between said first transmitting means and said first receiving means and between said second transmitting means and said second receiving means.

29. An elevator system according to claim 28 wherein said connecting means is a flexible transmission line having said first transmitting means and said second receiving means connected in parallel to one end thereof and having said second transmitting means and said first receiving means connected in parallel to the other end thereof.

30. An elevator system according to claim 28 wherein said transmitting means include means to generate a train of clock pulses, means responsive to said clock pulses for generating an enable signal and means responsive to said enable signal for coding each of said plurality of control signals in sequence.

31. An elevator system according to claim 30 wherein said means for coding includes multiplexing means responsive to said train of clock-pulses for selecting in sequence each of said plurality of control signals, said control signals being either a binary l or a binary 0; and means responsive to said train of clock pulses and said selected control signal for generating a four pulse coded signal having as the first and fourth pulses binary 0, the second pulse binary 1" and the third pulse binary 1 if said control signal is binary or binary 0 if said control signals is binary l. 32. An elevator system according to claim 30 wherein said receiving means include means responsive to said coded control signals for generating clock pulses, means responsive to said clock pulses for generating an enable signal, means responsive to said enable signal for decoding said coded control signals and means for storing said decoded control signals.

33. An elevator system according to claim 32 wherein said means for generating clock pulses includes a timer with a timing period equal to the duration of 1% pulses of said coded control signals, means responsive to the second pulse of said coded control said transmitter.

Claims (34)

1. A control system for an elevator including an elevator car, a controller for said car, and drive means for driving said car between a plurality of landings served thereby comprising a first statiOn having elevator controls; a second station having elevator controls; a transmission line coupling said first station and said second station; a plurality of signal inputs at said first station; means to read said inputs individually in a predetermined order; a transmitter at said first station coupled to said transmission line for transmitting signals from said reading means in the order said signals are read; a receiver coupled to said transmission line at said second station; a plurality of signal storage means at said second station; means to couple signals from said transmission line individually to individual signal storage means in a predetermined order corresponding to the order said signal inputs are read by said reading means, said storage means corresponding to said signal inputs; and signal outputs at said second station from said signal storage means.

2. A control system according to claim 1 wherein said first station is on said elevator and said second station is associated with the controller remote from said elevator car; means on said car responsive to car position coupled to one of said signal inputs to apply a signal thereto; and coupling means to said drive means from said signal output of said second station for said storage means corresponding to said car position responsive signal input.

3. A control system according to claim 1 wherein said car includes an entry; a closure for said entry; means sensing the position of said closure in said entry and applying signals responsive thereto to one of said signal inputs; and coupling means to said controller for said car from said signal output at said second station corresponding to said closure position responsive signal input.

4. A control system according to claim 1 wherein said car includes an entry; a closure for said entry; controls for said closure for applying signals to one of said signal inputs; and coupling means to said controller for said car from said signal output at said second station corresponding to said closure control signal input.

5. A control system according to claim 1 wherein said car includes means for registering car calls for service to the landings by passengers within said car for applying signals to said signal inputs; and coupling means to said controller for said car from said signal outputs at said second station corresponding to said car call signal inputs.

6. A control system according to claim 1 including a plurality of means for generating different car operating signals mounted on said car, means coupling each of a plurality of said signal generating means to respective ones of said signal inputs as said first station; and coupling means to said controller for said car from said signal outputs at said second station corresponding to said signal inputs for said car operating signals.

7. A control system according to claim 6 including a traveling cable extending between said car and a fixed location in structure severed by the car wherein said first station is on said elevator car and said transmission line is incorporated in said traveling cable.

8. A control system according to claim 1 including means to sense the completion of the reading of predetermined inputs; and means to enable a repetition of the reading of said inputs individually in said predetermined order in response to said completion sensing means.

9. A control system according to claim 1 including encoding means to encode signals read by said signal reading means for transmission by said transmission line; and decoding means to decode encoded signals received by said receiver to a form for application to said signal storage means.

10. A control system according to claim 9 wherein said encoding and decoding means are for binary signals.

11. A control system according to claim 1 including a plurality of signal inputs at said second station; means to read said inputs at said second station individually in a predetermined order; a transmitter at said second station coupled to said transMission line for transmitting signals from said reading means at said second station in the order said signals are read; a receiver coupled to said transmission line at said first station; a plurality of signal storage means at said first station; means at said first station to couple signals from said transmission line individually to individual signal storage means at said first station in a predetermined order as received by said receiver at said first station; signal outputs at said first station from said signal storage means at said first station; means for enabling said transmitter at said first station while inhibiting said receiver at said first station; and means for enabling said transmitter at said second station while inhibiting said receiver at said second station.

12. A control system according to claim 11 including means for enabling said receiver at said first station while inhibiting said transmitter at said first station; and means for enabling said receiver at said second station while inhibiting said transmitter at said second station.

13. A control system for an elevator comprising a first station and a second station; transmission line means coupling said first station and said second station; a transmitter at each station adapted to generate a regular cyclic sequence of signals for discrete elevator operating functions; a receiver at each station adapted to receive a sequence of signals for discrete elevator operating functions corresponding to the sequence and functions of the signals generated by said transmitter of the station coupled thereto by said transmission line; and means to maintain each received signal for said receivers until said signal is altered during a regular cyclic sequence of signals from the transmitter from which it was received.

14. A control system according to claim 13 including a plurality of signal sources at each station for said signals for discrete elevator operating functions; signal encoding means at each station for encoding signals from said respective sources for said respective transmitters; and signal decoding means at each station for decoding signals received by said respective receivers for application to said signal maintaining means.

15. A control system according to claim 14 including scanning means for said transmitter at each station for scanning said sources at said station; signal latch means for said transmitter actuated during an initial portion of the scan of each source by said scanning means to latch the currently scanned signal; and means enabling said encoding means during a portion of the scan of each source by said scanning means which is subsequent to said initial portion to encode the latched signal.

16. A control system according to claim 13 wherein said transmitter at said each station and said receiving means at said station are connected in parallel to said transmission line means.

17. A control system according to claim 16 including means to inhibit reception by the receiver at each station during transmission of signals by said transmitter at said station.

18. A control system according to claim 16 including means to enable reception by the receiver at each station upon completion of each transmission of a cyclic sequence of signals by said transmitter at said station.

19. A control system according to claim 13 including a plurality of sources of discrete elevator operating signals at each station; said transmitter at each station including means for scanning the sources at said station in a predetermined sequence; means at each station for encoding each signal as it is scanned; said receiver at each station including means for scanning said signal maintaining means in synchronism with said scanning means of said transmitter at the opposite station; and means at each station for decoding each signal received by said receiver.

20. A control system according to claim 19 including means to generate clocking signals, said clocking signals actuating said source scanning meAns; and means actuating said encoder in response to said clocking signals and in synchronism with the scan of individual signal sources.

21. A control system according to claim 19 including means to define a signal characteristic of each encoded signal; and means for actuating said signal maintaining scanning means in response to said defined signal.

22. A control system according to claim 19 including means to define a signal characteristic of each encoded signal; and means for actuating said decoding means in response to said defined signal.

23. A control system according to claim 19 including means associated with the transmitter at each station to generate clocking signals; means to advance said source scanning means in response to said clocking signals; means to actuate said encoder in response to said clocking signals and in synchronism with the scan of individual sources; means to produce a signal characteristic of an encoded signal for each encoded signal; means associated with the receiver at each station to advance said signal maintaining scanning means in response to said characteristic signal from the transmitter at the opposite station; and means for actuating said decoding means in synchronism with the advance of said receiver associated scanning means in response to said characteristic signal.

24. A control system according to claim 13 including individual sequencing controls for said first and second stations for mutually exclusive enabling of said transmitter and receiver of each station.

25. A control system according to claim 13 including means to sense an absence of synchronism in the sequence of signals transmitted by the transmitter at one of said stations and the signals received by the receiver at the station opposite said one station.

26. A control system according to claim 13 including means at each station for said transmitter at said station for sensing the completion of a cyclic sequence of signals generated by said transmitter; means at each station for said receiver at said station for enabling said receiver at said station in response to completion of a cyclic sequence of signals generated by said transmitter at said station; means at each station for said receiver at said station for sensing the completion of reception by said receiver of a predetermined number of signals generated by said transmitter at said opposite station; and means at each station to recycle said sequence of signals generated by said transmitter for said station in response to the completion of reception by said receiver at said station of said predetermined number of signals.

27. A control system according to claim 26 including a timer defining an interval initiated upon enabling a receiver at a station and of a length exceeding the time required to complete reception by said receiver of said predetermined number of signals; and means responsive to expiration of said interval without completion of reception of said predetermined number of signals to recycle said sequence of signals generated by said transmitter for said station.

28. In an elevator system including an elevator car movable in a hatchway, a source of a plurality of first control signals in said car, a control unit responsive to each of a plurality of second control signals in said car, a prime mover, a fixed controller for controlling said prime mover in response to each of said plurality of first control signals, a source for said plurality of second control signals in said controller and a communication system for sending said pluralities of first and second control signals in multiplexed coded binary form between said car and said controller, said communication system comprising a first transmitting means for said coded first control signals, a second transmitting means for said coded second control signals, a first receiving means responsive to each of said coded first control signals, a second receiving means responsive to each of said coded second control signals and connecting meanS between said first transmitting means and said first receiving means and between said second transmitting means and said second receiving means.

29. An elevator system according to claim 28 wherein said connecting means is a flexible transmission line having said first transmitting means and said second receiving means connected in parallel to one end thereof and having said second transmitting means and said first receiving means connected in parallel to the other end thereof.

30. An elevator system according to claim 28 wherein said transmitting means include means to generate a train of clock pulses, means responsive to said clock pulses for generating an enable signal and means responsive to said enable signal for coding each of said plurality of control signals in sequence.

31. An elevator system according to claim 30 wherein said means for coding includes multiplexing means responsive to said train of clock pulses for selecting in sequence each of said plurality of control signals, said control signals being either a binary ''''1'''' or a binary ''''0''''; and means responsive to said train of clock pulses and said selected control signal for generating a four pulse coded signal having as the first and fourth pulses binary ''''0'''', the second pulse binary ''''1'''' and the third pulse binary ''''1'''' if said control signal is binary ''''0'''' or binary ''''0'''' if said control signals is binary ''''1''''.

32. An elevator system according to claim 30 wherein said receiving means include means responsive to said coded control signals for generating clock pulses, means responsive to said clock pulses for generating an enable signal, means responsive to said enable signal for decoding said coded control signals and means for storing said decoded control signals.

33. An elevator system according to claim 32 wherein said means for generating clock pulses includes a timer with a timing period equal to the duration of 1 1/2 pulses of said coded control signals, means responsive to the second pulse of said coded control signals for initiating said timing period; and means responsive to the end of said timing period for generating a clock pulse.

34. A control system according to claim 13 including a timer defining an interval initiated upon enabling a receiver at a station and of a length exceeding the time required to complete reception by said receiver of a predetermined number of said signals; and means responsive to expiration of said interval without reception of signals to recycle said transmitter for said station to transmit the sequence of signals generated by said transmitter.

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