David B Love

US Patent:

41601319, Jul 3, 1979

Filed:

Oct 7, 1977

Appl. No.:

5/840451

Inventors:

Pradeep P. Kaul - Rockville MD
Thomas H. Scholl - Rockville MD
Deepak R. Muzundar - Gaithersburg MD
Daniel R. Wendling - Gaithersburg MD
Bob D. Buschman - Gaithersburg MD
Michio Ikawa - Tokyo, JP
Akira Miura - Tokyo, JP
David A. Love - Silver Spring MD

Assignee:

Nippon Electric Company, Ltd. - Tokyo

International Classification:

H04Q 520

US Classification:

179 99M

Abstract:

An electronic key telephone system is disclosed that provides a plurality of telephone features and functions, while only requiring a four-wire line between the central equipment and each key-set telephone (KST) and a two-wire line between the central equipment and each single-line telephone (SLT). Linear delta coding and time division multiplex (TDM) techniques are used to eliminate the multiple pairs required in traditional private business exchange (PBX) systems between the remote key telephones and the control unit. In the present system, a microprocessor controlled TDM controller transmits and receives control signals serially to and from interfaces in the system for control purposes and also for establishing exchange of digitized audio information data between selected interfaces. The system thus exchanges digitized audio information directly between interfaces and provides control signalling between the TDM controller and the interfaces, with all of the exchanges being done in real time. Among other things, the system is compatible with all types of existing central office exchange lines.