Patent GB-1052828-A (GB)
IPC: H04J3/20
Abstract: 1,052,828. Automatic exchange systems; parametric amplifiers; superconductive circuits. SIEMENS & HALSKE A.G. April 29, 1964 [April 29, 1963 (2)], No. 17763/64. Headings H3B and H4K. In a time division multiplex exchange utilizing the resonant transfer method of signalling, first and second stores, pertaining respectively to first and second subscribers, exchange energy via two multiplex highways and two intermediate stores. The first store and one intermediate store are initially connected to one highway and simultaneously the second store and the other intermediate store are connected to the other highway whereby the intermediate stores receive any energy contained in the first and second stores. Thereafter the one intermediate store is connected to the other highway and the other intermediate store is connected to the one highway so as to complete the energy exchange process. In each of the embodiments the first and second stores comprise capacitors connected through low-pass filters to their associated subscriber lines. The intermediate stores may comprise inductors, capacitors, magnetic cores, superconductive coils or capacitive or inductive parametric amplifiers. The highways may include rectifiers and/or lumped or distributed inductances (Fig. 5, not shown) so that greater tolerances in the operation of the various switches can be permitted. The systems described are very similar to those disclosed in Specifications 1,052,826 and 1,052,827. Parametric amplifiers.-The capacitive parametric amplifier shown in Fig. 9 comprises four varactor diodes arranged in a bridge network. A pumping voltage E is applied to one diagonal of the bridge and the other diagonal is connected between earth and the points marked X or Y in Fig. 1. The capacitors are adjusted so that voltages at the pumping frequency do not appear on the highway. An inductive parametric amplifier having a pump source F is depicted in Fig. 10. These amplifiers may act as intermediate stores or they may be included in the transmission path between the stores S1, S2 (Fig. 1) and the highways. Their gain may be adjusted for each call in dependence upon the attenuation of the subscribers lines involved in the calls. The Specification refers to a number of journals from which further information concerning these amplifiers may be derived. Ferrite core store (Fig. 4).-Before such a store is connected to a highway it is pulsed via p1 in order to reset it to its " zero " magnetization state. When information is received from a line store the state of magnetization of the core varies (on the linear part of its characteristic) accordingly. At the relevant time the core is again pulsed via p1 so that read-out of the stored information to the other line store concerned occurs. Superconductive stores (Fig. 14).-Currents are induced in the superconductive coils Sa2 and Sb2 when coils Sa1 and Sb1 are pulsed from the line stores. At the relevant time, read-out windings are pulsed by generators Pa, Pb whereby a magnetic field is produced which nullifies the current flowing in the superconductor. The collapse of the current induces a pulse in the coils Sa1 Sb1 which is repeated to the appropriate line store. Normal operation.-During a first time-slot, a calling station's line store, e.g. Ca is connected via highway Mab to intermediate store S1 and a called station's line store, e.g. Cb is connected via highway Man to intermediate store S2. In the next time slot, store S1 is connected to Cb via highway Man and store S2 is connected to Ca via highway Mab, thus completing the energy transfer process. The rotary memories Uan and Uab contain respectively the addresses of the called and the calling parties. Monitor U1 checks the condition of the highways and monitor U2 that of the memories. Fault, operation.-If U1 detects say a shortcircuited highway or U2 a memory into which information is being fed at too rapid or too slow a rate, the control circuit responds and initiates single multiplex highway working. For this purpose the addresses stored in the faulty memory (or the memory associated with the faulty highway) are transferred to the other memory. Three positions are required in a memory for the addresses pertaining to a call so that some of the calls may have to be broken down. It is suggested that calls involving priority subscribers (e.g. those making interexchange calls or certain PBX subscribers) should be provided with adjacent vacant positions in the memory at least under low volume traffic conditions whereby if a fault occurs these subscribers are assured of a continuous connection. In any case the working memory say Uab now opens line gate abta say, during a first time slot so as to connect Ca to S1. In the next time slot gate abtb is opened and 1k2 is closed to connect Cb to S2 following which 1k2 is opened and 1k1 is closed to connect S1 to Cb. In the next time slot abta is again closed to connect S2 to Ca via 1k2 thus completing the energy transfer process. In an alternative embodiment a plurality of intermediate stores are provided whereby the necessity of using succession time slots for each call is overcome (Fig. 12, not shown). Interconnecting subscribers connected to different pairs of highways. Although no details are given it is suggested that this may be achieved by means of further intermediate stores which are alternately connectible to the relevant highways of the two pairs in a similar manner to the method described above in which two lines are connected to two highways to which two intermediate stores are alternately connected.