Multimode modem

[54] MULTIMODE MODEM

[75] Inventor: John A. Greszczuk, Roslindale, Mass.

[73] Assignee: Codex Corporation, Canton, Mass.

[21] Appl. No.: 192,952

[22] Filed: May 12, 1988

[51] Int. CU H04B 1/38

[52] U.S. CI ;375/8; 375/121;

379/63

[58] Field of Search 375/7, 8, 9, 13, 36,

375/39, 121; 379/93, 97, 98; 370/24, 31, 41, 43, 29, 110; 178/2 R, 3

[56] References Cited

U.S. PATENT DOCUMENTS

3,716,672 2/1973 Fretwell 375/8

3,842,207 10/1974 Fretwell 375/8

4,215,243 7/1980 Maxwell 379/98

4,578,796 3/1986 Charalambous et al 375/8

4,727,370 2/1988 Shih 375/106

4,756,007 7/1988 Qureshi et al 375/8

OTHER PUBLICATIONS

"A Proposed Appendix to Recommendation V. 32 Interworking Procedure with V. 22 BIS and V. 32 Modems", Study Group, XVII Geneva, 21-25, Apr. 1986.

Primary Examiner—Benedict V. Safourek
Attorney, Agent, or Firm—Fish & Richardson

[57] ABSTRACT

The modem communicates with a variety of modem types employing differing initial handshake signals. The multimode modem sends a sequence of signals corresponding to the variety of modem type handshake signals and the sequence terminates when the multimode modem receives an appropriate response identifying a particular one of the variety of modem types.

16 Claims, 4 Drawing Sheets