Circuit arrangement for exchange of signalling between telephone switching systems interconnected as primary and secondary systems

摘要

In the circuit arrangement for exchange of signalling between telephone switching systems interconnected as primary and secondary systems, in particular PBX systems, on both sides of the secondary connection line within the line circuit connected thereto, in each case a ready-to-receive modem is linked using a four-wire connection via a hybrid circuit to the two-wire connection path. The signalling exchange itself is performed according to a frequency shift keying method recommended by the CCITT, a data word in each case being serially transmitted after the transmission of a send signal. The information contained in a data word of this type can be directly assigned to a feature so that a control device located in the line circuit can evaluate the data word in order to effect switching processes, the data word within the switching system concerned being further processed or temporarily stored. The ready-to-receive modems are in each case linked using a four-wire connection via a hybrid circuit to the two-wire connection path, this hybrid circuit being formed either by the switching of electronic switching points or by an active hybrid resistance circuit.