GB1395193A - Telecommunications exchange systems - Google Patents

Abstract

1395193 Automatic exchange systems SIEMENS AG 30 Aug 1972 [30 Aug 1971] 40102/72 Heading H4K In an exchange system in which some of the subscribers have two different transmitter/ receiver units, e.g. a telephone set and a data unit, and in which the priority afforded to the connection is dependent on the particular transmitter/receiver unit in use, a priority store associated with the exchange junctor supervising the connection is arranged to be updated when a subscriber switches from one transmitter/receiver unit to the other during an existing connection. This enables for example a break-in inhibition to be introduced when a data unit is switched in without a break in the connection following a normal telephone conversation between two subscribers. The arrangement is particularly applicable to PBX's. It may also allow different metering rates for normal and data calls to be charged. As shown diagrammatically two subscribers are interconnected via subscriber line circuits TS1, TS2, switching stages KF1, KF2 and a junctor Ue, having associated therewith a signal analyser AW, a pulsing device TK and a memory BK in which the priority of the connection associated with the junctor is stored. The change in priority is initiated by the operation of the subscriber switches W1 or W2, either manually or automatically, this operation being signalled to the junctor using A.C. or D.C., e.g. impedance, signalling. Separate signalling wires may be used for this purpose. The junctor may in fact intercept a signal from subscriber station 1 to subscriber station 2 which signal is indicative of the switching in or out of the data unit. Where D.C. signalling is used the junctor may be provided with a line transformer to enable D.C. signals to be intercepted. Alternatively the junctor may intercept a preliminary data signal, this being achieved using a transformer winding and filters or the junctor may detect the change in line impedance that will occur when a switch from a speech to a data unit or vice versa takes place. In addition to changing the break-in criteria, the switching of the priority may also be used to initiate a change in charge rate, e.g. when a data unit is switched in, a change in the metering pulse train may take place in such a fashion that a trunk connection is simulated i.e. the call is charged at a higher rate.