| 摘要 |
<p>Telephone system including a central exchange (EX) to which a plurality of telephone sets (TA) are connected via two-wire lines, for transferring digital information in time-division form between the sets. The system is entirely digitized and contains a central processor board (EXCP) in the exchange with a central processor (CP) and memory units common to the system, a plurality of speech control boards (CCDX), and a plurality of line boards (LIDI). Each of the speech control and line boards contain a regional processor (RP) inconnection with the central processor through a control bus (SB) specially arranged for control signalling. Each speech control board contains a plurality of speech control units (SC) and each line board contains a plurality of line circuits (DEC). The speech control units and line circuits are connected to an internal communication bus (TB) for transferring pulse code modulated information between the telephone sets (TA). Two 2-wire lines are connected to each line circuit (DEC), each two-wire line corresponding to a telephone set. In each telephone set there is included a further line circuit (DIC) containing, inter alia, means for coding and decoding PCM signals. An advantage with the system is that it lacks central switching equipment for channel selection. Channel selection menas (CHR) are included in said first line circuits (DEC), with the aid of the regional processor (RP), said means connecting the lines to channels determined by the central processor under control of said central processor. The system futhermore relates to a multichannel system (each channel corresponding to time slots in a time multiplex system), in which each channel is divided into two halves, a microphone half and a loudspeaker half such that two subscribers can be connected directly to each other on the same channel. A channel can be made common for all telephone sets and can, for example, be divided into a channel half for silence and a channel half for tone signalling.</p> |
