US2312127A - Photoelectric controlled oscillator device - Google Patents

Description

Feb, 23, 1943. F. H. SHEPARD, JR

PHOTOELECTRIC CONTROLLED OSCILLATOR DEVICE Filed Nov. '7, 1939 Rm, .w m R m m m T A H m C M m J n Y wEEB B m QN/ 1| w n xwmm dun LEG Ill. L L-EEQ F4463 mkmxmm mm lllll IL L L m 566% @T d I I I I I I I l l I I I I I l l I l I I l Ill u x o E M23 mmkom the same power line at convenient Patented Feb. 23, 1943 rnoronancrnrc coN'rRoLLnn osomaaron DEVICE Francis H. Shepard, Jr Merchantville, N. (5., assignor to Radio Corporation at America, a corporation of Eel-aware Application November 7, 1939, Serial No. 303,191

4 Ciaims. (Cl. 177-352) My present invention relates to oscillators controlled by photo-electric devices, and more particularly to alarm systems utilizing light-controlled oscillator circuits for generating a signal wave capable of being detected it a point remote from the oscillator.

One of the main objects of my invention is to provide an alarm system in which capacity and photo-electric units may be plugged into the nearest alternatin current outlets of a. power line, and made to place a signal wave on the power -line on the approach of an intruder whereby a large residence, store, warehouse or ofllce building can be protected without the necessity of costly installation wiring costs.

Another important-object of this invention is to provide a signalling system wherein a lightcontrolled oscillator is connected to a power line for energization, and the power line functioning as a wave transmission line as well; one or more signal wave indicator-devices being lugged into places remote from'the oscillator.

Another object of my, present-invention is to provide burglar alarm systemswhich dispense with the need forexpe'nsive wiring installations, and wherein the signalling device is a photo-electrically controlled oscillator which is plugged into thee'x'isting power line; a simple one-tube relay alarm circuit being plugged into the power line atany desirable remote point to indicate the si naljoscillations transmitted over the power line. Still other objects of this invention are to improve generally. the simplicity and efflciency of burglar alarm systems, and'moreespecially to provide an alarm system which is not only dur-- able and reliable in operation, but is'economical to manufacture and install.

The novel features which I believe to be characteris'tic of my invention are set forth in particularity in the appended claims; the invention itselLhowever, as, to both its organization and m i e bd of operation will best be understood by reference to'the following description taken in connection with the drawing in which I have indicated diagrammatically a circuit organization whereby my invention may be carried into eflect.

Referring now to the accompanying drawing, I there. is shown a power line I ;-which is to be understood as transmitting 60 cycle current through a structure such as; a large residence, a store, warehouse or an omce building; I Assume that the room, or area, where-socket 2 islocated is to be protected against intruders. There is. then, plugged in o t e; wi ket. t e p on s a plus 8.

which functions to provide the means for feeding energizing current to the tubes of the oscillator, and which also acts to transmit the signalling oscillations to the power line i for transmission to one or more remote points. The light-controlled oscillator comprises an oscillator tube 4 which may be of the 25A6G type.

This type of tube may be a .pentode employing an indirectly heated cathode. The tube t includes the anode 5, cathode 6, control grid l, intermediate grid 8 and suppressor grid 9. Both the heater filament l and cathode s are tied to the lead I: which is connected to one terminal of the plug 3.

The plate is connected to the other terminal of plug 3 through a path including coil l2 and lead Hi. The grid 2 is tied to the lead It), while grid 9 is tied to the cathode B. The coil l4 connects cathode dto the control grid l through blocking condenser I5. The adjustable condenser l6 connects the coils It and I2 in series, and

' acts to resonate the oscillator to the operating frequency desired for the signal waves to be transmitted over power line i. Coils l2 and M are strongly coupled by the condenser l6. The tube ll, which may be a pentode of the 6J7 type, acts as an amplifier for the output voltage of and hence is used to biasthe grid 1 of oscillator sistor 32. The latter is included in series with the photo-electric tube l8. The latter may be a phototube of th 922 type, for example. Tubes I1 and l are connected back to back; the potential of plate 21 is negative with respect to line H 4. The anode IQ of the phototube is connected to lead II. The cathode is connected to a movable tap 2!, the latter being adjustable along cathode resistor 22, through resistor 23 and condenser 24 arranged in series. Condenser 24 increases the sensitivity of the device, and eliminates instability due to contact potential variations. The cathode end of resistor 23 is connectvecl by lead 25 to the control grid 26 of amplifier ll. The plate 21 is connected through resistor 28 to lead I l, condenser 29 by-passing the resistor. The anode end of resistor 28 is connected by resistor 30 to grid 1. The screen grid of tube I1 is connected by slider 3! to any desired point on rethe heater elements 33=and to. The cathode 34 is tied to filament 33, and the latter is connected to lead IS. The condenser 35 by-passes that portion of resistor 32 between tap 3| and cathode 34, whilecondenser 36 by-passes the cathode resistor 22.

There is provided a light source 40 which projects a. beam of light it upon the cathode 20 of -photo electric tube 98. The tap 2| is adiusted along resistor 22 towards the bottom thereof with light on the cathode 20. The tap 2| is now moved towards the top thereof past the point at which the oscillator l is prevented from oscillating. If. now, any obstacle is placed between the light source 40 and the phototube l 8 which cuts of! the light beam 4!, oscillations will again commence. These oscillations, or waves, are impressed upon the 'power line i and transmitted over the power line. At a remote room, or area, there islocated any desired type of detector 50 followed by arelay device 5 I, the latter operating any desired indicator 52. It will, therefore, be understood that the rectangle designated "represents a remote location at which point an indicator or alarm device is connected to the power line to respond to the oscillations transmitted over the line. .The

detector may consist of a single tube connectedto function as the usual detector of unmodulated carrier waves, andthe relay and indicator device can be of any well known construction. The incondensers II and 88 as shown, and by shielding the grid wires of tube ll, a.back-lash eifect is eliminated. This latter eifect is due to a radio frequency feedback to the tube II. With "backlash eifect eliminated, and a fairly stable power line, the circuit will operate satisfactorily for small light changes. If the line has large voltage variations it is wise to make the circuit insensitive to small light changes. This is normally easily provided for in relay operation. If high light intensities are'used (more than 0.l lumen) the cathode of tube II and the upper end of resistor 22 should be returned to a higher point on resistor 32. The indicator 2 can be in the form of a light, floodlight, bell. a siren, an annunciator, or any other well known device.

The following constants are given for the oscillator network by way of illustration, and it is to be clearly understood that these figures are in no way restrictive:

While l have indicated and described a system for carrying my 'invention into effect, it will be pass over the power line. It is to be understood 7 that the frequencies may be in the :audio, or radio ranges. In general, when thebeam of light ll is interrupted by an intruder or obstruction the alternating current-bias qn the grid 26 of the amplifier tube l'l cuts off the plate current of the tube. This causes the voltage drop across the plate load resistor 28 to decrease thereby removing the negative voltage from the grid I of the oscillator tube. Such removal of negative voltage allows the oscillator tocommence oscillating, and the oscillator voltage is impressed upon the power line throughthe oscilappaarent to one skilled in the art that my inlator tank circuit which is series resonant with l negative part of the alternating current cycle the condenser tends to charge up by drawing grid current to the peak voltage betweencathode 24 and the setting of tap 2|. On the active positive half-cycle the voltage on the grid is equal to the voltage across the condenser due to that condenser charge plus the alternating current voltage applied through the condenser organization shown and described, but that many modifications may be made without departing fromthe scope of my invention, as set forth in the appended claims.

What I claim is: V 1. In combination with an alternating current power line, an oscillator network, light-responsive means for normally preventing oscillation production by said network, means for connecting'said network to said power line for energisation of the network with alternating current from said line, means for coupling said network in oscillation energy transfer relation to said line whereby the line-functions as .the transmission medium for the oscillations, means connected to said power line at a point remote from said network for indicating oscillations transmitted over said line iromsaid network, said light-responsive means including a light source,

a phototube having light from said source impressed thereon, and a tube energized bysaid power line and-responsive to current ilow from resistor 22 minus the drop in the resistor 23 determined by the amount of light on phototube It. Thus, when there is plenty of light on the phototube the grid 26 is eifectively above cut-oil, and the tube 11 draws plate current thereby charging the condenser 29 negative. This negative voltage cuts oil the oscillator tube through the path including resistor 3!, and thus no oscillation pulses are put'onthe power line.

through said phototube for rendering's'aid oscillator network inoperative.

2. In'combination with an alternating "current power line, an oscillator network, light-responsive means for normally; preventing oscillation production by said network, means for connecting said network to said power line for energiza- 'tion of the network from .said line, means for coupling said network in oscillation energy 1 transfer relation to said line whereby the line functions as the transmission medium for the oscillations, means connected to said power line at a point remote from said network for indicating oscillationstransmitted over said line from said network; said oscillator network ineluding a tube having-input and output electrodes coupled to provide said oscillations', a second tube having an output circuit arranged to control the potential difference between oscillator tube input electrodes, said energization means applying alternating current from said line to both said tubes to energize them, and said light-responsive means including an element for controlling the conductivity of said second tube. v

3. In combination with an alternating current power line, an oscillator network, light-responsive means for normally preventing oscillation production by said network, means for connecting said network to said power line for energization of the network with alternating current from the iine, means for applying said oscillations to said line whereby the latter acts as a transmission line for the oscillations, means connected to 'said power line at a point remote from said network for indicating oscillations transmitted over said line from said network, said oscillator network including a tube having input and output electrodes coupled to provide oscillations of a predetermined frequency, a sec. ond tube having an output resistive impedance arranged in its space current path, means to apply voltage developed across said impedance to said oscillator tube input electrodes in a cutoff sense, said second tube including a control electrode, said light-responsive means including a photo-electric tube having a control connection to said control electrode such that space current flows normally through said resistive impedance.

4.121 combination with an alternating current power line, an oscillator network, lightresponsive means for normally preventing oscillation production by said network, means for connecting said network to said power line for energization of the network with alternating current from the line, means for applying said oscillations to said line whereby the latter acts as a transmission line for the oscillations, means connected to said power line at a point remote from said network for indicating oscillations transmitted over said line from said network, said oscillator network including a tube having input and output electrodes coupled to provide oscillations of a predetermined frequency, a second tube having an output resistive impedance arranged in its space current'path, means to apply voltage developed across said impedance to said oscillator tube input electrodes in a cut-off sense, said second tube including a control electrode, said light-responsive-means including a photo-electric tube having a control connection to said control electrode such that space current flows normally through said resistive impedance, and connections from said line to the electrodes of each of said oscillator tube, second tube and photo-electric tube thereby to energize them with said alternating current.

FRANCIS H. SHEPARD, JR.

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