System for processing channel signalling in a time-division digital exchange

A system for processing channel signalling in a time division digital exchange for switching at least some telephone channels including channels switched on a demand basis and tie-line channels connected on a semi-permanent basis, the exchange including:

• microprocessor control units;
• a switching network;
• and microprocessor terminal units;
• said control units and said terminal units being connected to said switching network via two-way multiplex lines enabling said terminal units to be controlled by said control units and also enabling said terminal units to communicate with one another;
• said terminal units including digital circuit terminal units serving respective PCM junctions via respective digital circuits and said exchange including at least one mixer and separator means for storing information defining tie line cross connections passing through the exchange;
• the improvement wherein said system for processing signalling comprises means for serving communications channels both on a demand basis and on a tie line basis, said means being incorporated both in said digital circuit terminal units and in said mixer and separator means and comprising for each of said digital circuits:
• a digital terminal to perform transcoding and frame realignment;
• a signalling receiver circuit for receiving channel by channel signalling from said PCM junction connected to said digital circuit and for forwarding to said mixer and separator means at least the tie line signalling relating to channels in said PCM junction which are used on a tie line basis;
• and
• a signalling and alignment circuit serving firstly to monitor in parallel the alignment of the multiframes coming from the PCM junction connected to said digital circuit and from the mixer and separator means receiving said tie line signalling, and secondly for transmitting said tie line signalling to the PCM junction served by said digital circuit, wherein said mixer and separator means is constituted by at least one mixer and separator terminal unit receiving the signalling channels associated with the tie line channels coming from PCM junctions connected to the exchange and forwarding via said switching network said tie line channel signalling to appropriate digital circuit terminal units for retransmission over their respective associated PCM junctions.

A system for processing channel signalling in a time division digital exchange for switching at least some telephone channels including channels switched on a demand basis and tie-line channels connected on a semi-permanent basis, the exchange including:

• microprocessor control units;
• a switching network;
• and microprocessor terminal units;
• said control units and said terminal units being connected to said switching network via two-way multiplex lines enabling said terminal units to be controlled by said control units and also enabling said terminal units to communicate with one another;
• each said terminal unit comprising a time switch connecting the unit to the switching network of the exchange via two-way multiplex links, said terminal units including digital circuit terminal units serving respective PCM junctions via respective digital circuits and said exchange including at least one mixer and separator means for storing information defining tie line cross connections passing through the exchange;
• the improvement wherein said system for processing signalling comprises means for serving communications channels both on a demand basis and on a tie line basis, said means being incorporated both in said digital circuit terminal units and in said mixer and separator means and comprising for each of said digital circuits:
• a digital terminal to perform transcoding and frame realignment;
• a signalling receiver circuit for receiving channel by channel signalling from said PCM junction connected to said digital circuit and for forwarding to said mixer and separator means at least the tie line signalling relating to channels in said PCM junction which are used on a tie line basis;
• and
• a signalling and alignment circuit serving firstly to monitor in parallel the alignment of the multiframes coming from the PCM junction connected to said digital circuit and from the mixer and separator means receiving said tie line signalling, and secondly for transmitting said tie line signalling to the PCM junction served by said digital circuit;
• wherein each digital circuit terminal unit includes inlet multiplex links and outlet multiplex links connecting the time switch of the digital terminal unit to the signalling receiver circuit, to the signalling alignment circuit and to a transceiver of the unit's microprocessor, the time switch establishing connections of these circuits between one another and with the multiplex links connected to the switching network for the purposes of signalling and under the control of the microprocessor.