SE333755B - - Google Patents

Abstract

1,205,307. Automatic exchange systems. SIEMENS A.G. 18 Oct., 1968 [1 Dec., 1967; 26 July, 1968], No. 49397/68. Heading H4K. In a stored programme controlled exchange in which the peripheral equipments are arranged in groups each of which has its own control circuit, i.e. effectively a plurality of centrally controlled PBXs, communication between the equipments and the control circuit is effected over a common bus which starts and terminates in the control circuit and to which the equipments are selectively connectible. The ends of the bus are connected by a comparator so that information sent into the bus can be compared with information received therefrom whereby a fault signal can be generated in the event of any discrepancy. The system forms part of that described in Specifications 1,205,305, 1,205,306, 1,205,308, 1,205,309 and 1,205,301. The individual equipments JG1-JGn each contain a plurality of senders (e.g. contacts such as s1) and receivers (e.g. relays such as E1), the equipments being selectively connectible to a space or frequency division multiplex bus U11 by relays Mo1 to Mon under the control of an identifier Jd in the group control circuit AS. Serial data from a central control is stored in sender SS prior to despatch in parallel form over bus U11 to the selected equipment. The accuracy of the data after it has traversed the bus and been received back in receiver ES is determined with the aid of comparator Vg. Parallel data from an equipment is converted into serial data by receiver ES for subsequent transmission to central control and is temporarily stored in VS. When data sending from the equipment stops, the stored data in VS is sent round the bus so that the efficacy of the latter can be checked. As an alternative to comparing the whole of the transmitted data with the received data, the parity of the former data may be determined and stored for later comparison with the parity of the received data thereby reducing the duration of the connection with central control and/or reducing the amount of storage space required in the control circuit (Fig. 4, not shown).