| 摘要 |
1409160 Automatic exchange systems STANDARD TELEPHON UND RADIO AG 17 May 1973 [25 May 1972] 23525/73 Heading H4K An interface between a stored programme controlled processor and a switching system incorporates a last-look memory for monitoring the condition of subscribers lines and trunks connected to the switching system so that applications to the processor are only made in respect of lines that have experienced a change in state. As shown the system comprises a plurality of analogue telephone stations connected by concentrators A-Kz to PCM terminals T, a plurality of digital and data stations connected directly to PCM concentrators D-Kz, a plurality of conventional inter exchange trunks (LF lines) connected to PCM terminals T, and a non- blocking TDM switching assembly DE. The latter interconnects the various terminals and gives them access to registers WE and also to interfaces TE. The PCM links utilize 30 channels for intelligence signals, one channel for synch. purposes and one for control data. Each terminal is connected to an interface via a semipermanent control channel through the network. The control data consists of two bits in respect of each line or trunk terminated on a terminal and two bits for the terminal itself. The meaning attributed to the two bits may differ in dependence on the connection state of a line viz. free, busy, calling, ringing, dialling &c. If central control ZS so decrees, the whole of a control channel may be temporarily taken over in order to interrogate a particular line and to receive a detailed answer concerning the line. It is essential that the lines and trunks be scanned fairly rapidly so a condition is imposed that between each exclusive use of a control channel by central control, a scan of the lines monitored via that channel be instituted. |
