Special facilities accessing appts. for telephone exchange - has subscriber dialled code recognition circuitry to release normal exchange function connections and route to special facilities equipment

摘要

The telephone exchange subscriber line circuit additional special service facilities is arranged so that the subscriber (T) has normal speech service via the exchange line (TAL) through contacts (i) in the special facilities unit (STS) and onto the exchange 'a' and 'b' wires connecting the subscriber into the line-finder (AS) and finals multiple (LW). Control switching (TS) is also coupled via the 'c' wire. The special services circuitry (STS) comprises a dialled code recognition circuit (WE) so that the subscriber dialled code used to initiate the circuit is recognised. Evaluation circuitry (AW) compares the dialled code with stored commands (SP) to determine the facility required. A data highway (DL) is used to transmit the subscribers request into the announcement equipment (AE) via a receive modem (DV). The subscriber's line (TAL) is then disconnected in the special facilities equipment (STS,i) and special services switching equipment (SN) connects all incoming calls to that subscriber through to the announcement equipment (AE). To restore service the subscriber (T) dials a further code into the recognition circuit (WE).