GB1045687A - Improvements in or relating to time division multiplex communication systems - Google Patents

Abstract

1,045,687. Automatic exchange systems. SIEMENS & HALSKE A.G. July 17, 1963 [July 18, 1962], No. 28232/63. Heading H4K. In a time division multiplex communication system, metering pulses in respect of a call are inserted into a circulating memory during the same time slot as that in use for the call. The addresses of the calling and called subscribers are stored in circulating memories Ua and Ub respectively whereby the appropriate line gates S1 to Sx or trunk gates SL1 to SLx may be opened synchronously during the time slot allotted to the call. The memories consist of magnetostrictive delay lines having associated amplifiers for inserting, reinserting and deleting pulses relevant to a call during the corresponding time slot. In the case of a local call, a metering pulse is inserted into circulating memory Uz (section tzm) from control unit E upon the reply of the called subscriber, and upon termination of the call the address of the calling subscriber is passed via switch SR1 to a recorder, e.g. a magnetic tape, of a subscriber's meter under the control of the circulating pulse in Uz. In the case of a trunk call, e.g. from a PBX to a main exchange, incoming metering pulses on the relevant trunks FL1 to FLx are transmitted via a transfer unit such as Ue1 and metering bus ZM to the control unit E where they are processed and injected successively into memory Uz. Provision is made in unit E for ensuring that only one pulse is inserted into Uz for each metering pulse on a trunk since in general each such pulse will be sampled more than once during the successive scanning of the line circuits T1 to Tx and transfer units Ue1 to Uex by the control unit. If only one delay line, e.g. tzm, is provided in the memory, the address of the calling subscriber must be recorded before a new pulse can be inserted so that provision is made for reading the memory between the metering pulses occurring on the trunk. Alternatively by providing a plurality of delay lines the successive pulses may all be temporarily stored and at the end of the call, the contents of the memory then passed via switches SR4, SR2 and SR3 (the identity of the called subscriber in a toll or trunk call being recorded in Ud) to a call-charge-assessing device DR, e.g. a PBX operator or an automatic ticketing device. The system may be one in which each subscriber is permanently allotted a particular time slot.