Subscriber line transmission of messages to telephone station - has system substituted for direct link between two lines using two-input mixer respectively receiving message and service signals

摘要

The transmission system is incorporated in a telephone installation having a service signal generator of special currents for e.g. dialling, callback, routing, holding or calling purposes, sent to each subscriber station lifting its handset to request connection with another station. The system includes a mixing transformer with two prim. windings connected respectively to the service signal generator and to a message generator via an attenuator, changeover switches, a circuit for synchronising service signals and message transmissions, and a transformer. Another switch allows the synchronising circuit to be taken out of this connection. The output of the mixing transformer is switched to the telephone line of the subscriber requesting connection. The system may provide facilities for video telephone, data bank access etc.