Patent GB-1280045-A (GB)
Title: Improvements in or relating to telecommunication exchanges
Inventor: THOMAS DAVID MICHAEL
IPC: H04M3/56
Filed: 1969-10-21
Abstract: 1280045 Automatic exchange systems STANDARD TELEPHONES & CABLES Ltd 16 Oct 1970 [21 Oct 1969] 51629/69 Addition to 1234419 Heading H4K  In a switching system in which incoming time-division-multiplex highways are switched over at least one intermediate highway to outgoing highways, channels of the intermediate highway are set aside for the sole purpose of connecting incoming channels to a conferencing circuit CC, the talking one of the conferees being identified by CC so that his channel on the intermediate highway may be connected over path CH, gate HGN, and intermediate highway channel switches P to the outgoing channels of all other conferees, the gate HGN being used to block the path CH so that the talking conferee does not receive his own speech. The switching system has forty incoming highways LI of twelve channels apiece and supermultiplexed on ten intermediate cross-office highways HW. Each highway HW gives access to a group of five outgoing highways LO. Delta-sigma modulation is employed and for each time slot on an outgoing highway the intermediate highways have six minor time slots, five minor time slots being channels corresponding to the same concurrent time slot on each of the five outgoing highways and the remaining minor time slot providing time for writing incoming channel data on stores MS. Gating from the stores MS and conference circuit CC on to the intermediate highways is effected by a cyclic store CS for each highway. A store CS has a storage section for each minor time slot on its highway corresponding to a channel on an outgoing highway. The presence of an incoming channel address in a storage section effects operation of the inter-highway gates to connect the incoming store MS to the outgoing channel corresponding to the associated minor time slot. The fifth outgoing highway of each group LO and the corresponding fifth minor time slots on the intermediate highways are reserved for conference connections, only three channels of each highway being used to provide a 30 channel conference capacity. Subscribers are connected in conference by inscribing their incoming channel addresses in the fifth minor time slot sections of stores CS to get access to inlets of the conference circuit CC with channel stores SS. The active talker is detected and indicated by a channel marker Q, such as 1Q3, the operated marker Q acting on a decoder DC to identify the intermediate highway over which the talker's modulations are received and to apply such an identifying pulse R in the talker's fifth minor time slot to a gate TG to obtain the talker's incoming channel address from CS. A translator converts this address to a pulse in the talker's outgoing channel minor time slot position to inhibit HGN so that he does not receive his own speech but is connected instead to an idle code generator which demodulates as silence. The storage sections in stores CS of outgoing channels of all conferees contain addresses to operate conference circuit to intermediate highway gates P so that, with the exception of the talker himself, all conferees receive the output of the conference circuit. The stores CS may be constructed as integrated circuit memory elements or with ferrite memory elements.