William E. Cheal - San Jose CA
Gokal C. Gupta - Fremont CA
Faramarz Sepahmansour - Milpitas CA
Avnish K. Aggarwal - San Jose CA
Northern Telecom Limited - Nashville TN
A subscriber loop system in association with a TDM telephone system provides voice and data communication with a remote telephone station set and an associated data port. The subscriber loop system includes a voice path and a data path. Supervisory and signalling circuits in the telephone set are used for generating and registering call control signals pertaining to both voice and data calls. The call control signals are labelled and multiplexed with data signals by local and remote line interface circuits for transmission therebetween. A codec in the voice path is caused to couple call progress signals (i. e. dial tone, ring back) to the telephone set during a data call progress, for audible signalling to a user. Changeover relays are connected in combination with the data path and the line interface circuits such that the line interface circuits are bypassed in the event of power failure of the remote line interface circuit, to provide a more direct connection between the signalling and supervision circuits and the TDM telephone system whereby ordinary voice telephone service is maintained in the event of such failure.