GB1027316A - Improvements in or relating to time-division multiplex telecommunication systems - Google Patents

Abstract

1,027,316. Automatic exchange systems. SIEMENS & HALSKE A.G. Feb. 4, 1963 [Feb. 2, 1962], No. 4497/63. Heading H4K. A time division multiplex exchange system is provided with means for diverting calls intended for certain subscribers to predetermined other subscribers. In the PBX system described a free time slot, e.g. P1 is allocated to a calling subscriber, e.g. N1 whose identity is then recorded in a " circulating " memory Ua whereby during this time slot a pulse is provided by Ua and decoder Da to open the subscriber's speech gate SN1. Similarly, the identity of the called subscriber is recorded in Ub during this time slot. The condition of every subscriber equipment in the system is examined in turn by means of a scanner AZ which provides a marking representative of the subscriber equipment number on its output A2. This marking, which persists for 100 Á secs. or 200 Á secs. in dependence upon whether the condition of the equipment in question has changed in the interval between two observations, is applied to translation field UM which provides at its outputs inter alia the directory number of the subscriber or the diverted directory number. Operation.-The closure of a subscriber's loop, e.g. N1 is signalled over multiplex highway SMN to the control circuit ST when AZ " reaches " this subscriber during its scanning cycle. The subscriber's identity as provided by AZ and UM is compared by means of comparators RA, AA, RB, AB (Fig. 4, not shown), with the identities recorded in memories Ua and Ub so that if no coincidence occurs a free time slot P1 is allocated to the caller, gate DS<SP>11</SP> is opened in order to record his equipment number (from AZ) at position P1 in memory Ua and a pulse, also at P1, is inserted in a memory Uda. A free digit-receiver MM is then allocated to the call and the caller signals using a V.F. code the special digit indicative of a desire to set-up a diverted call condition. At time P1 this digit is translated into a binary code and transmitted direct to memory Ub. When AZ reaches N1 again, signals on a/va from Ua and on k1 from Ub are applied simultaneously to the control circuit ST (Fig. 5, not shown), whereby marking pulses at time P1 are recorded in " rotating " memories UK and Uti the latter of which causes a special tone to be reverted from TZ to N1. A pulse on lead l erases the special digit from Ub. The caller then dials the number of the station to which his calls are to be diverted and this number is stored at P1 in Ub. Consequently, when AZ sets to N1, markings on wire b from Ub and on wires a/va and uk are sent to the control circuit whereby the pulses circulating in UK and Uti are cancelled and gate D1 is opened so as to allow the identity of the diversion station to be transmitted to UM and recorded therein on magnetic cores. By dialling another special code the subscriber may cancel the diverted call condition. The Specification also describes a system in which the number of the diversion station is permanently recorded in UM so that the subscriber need only dial a special digit in order to have his calls diverted to this station. In setting up a call the subscriber dials the wanted directory number (this being rewritten as an equipment number when AZ sets to the called subscriber) into store Ub via MM, at the time position P1 allotted to the call and circuits AZ, UM, ST then inject a pulse into memories Uda, Udb at P1 so that gates Sp1 and Sp2 are opened simultaneously whereby the equipment numbers circulating at this time in Ua and Ub can be translated by Da and Db into station marking pulses which are applied to the speech gates SN1 and SN2. In the event of a call to a main exchange, junction circuits A-U are allocated appropriately. The rotating memories Ua, Ub &c. consist of magnetostrictive delay lines having transistorized driving circuits and the decoders Da, Db consist of rectifier matrices (Fig. 3, not shown).