GB1279507A - Pcm switching system - Google Patents

Abstract

1279507 Automatic exchange systems INTERNATIONAL STANDARD ELECTRIC CORP 24 Sept 1970 [30 Sept 1969] 45509/70 Heading H4K In an electronic P.C.M.: T.D.M. tandem highway switching system, interhighways can be split to provide go and return signal paths between a channel on the split highway and a central control. The figure is divided by a horizontal line and shows below that line equipment common to all highways only one of which is shown above that line. In the normal switching mode speech signals incoming over the highway are converted from serial to parallel form at 3 and entered in a location in a random access speech signal store SS and are gated at appropriate moments via an 8 conductor interhighway 5a and 5b to the appropriate outgoing highway via a parallel to serial converter 4, the storage addresses being determined by address decoders 7 and 8. The decoder 8 receives its address signals from a switching memory 1, the locations of which are read out successively under the control of a clock signal generator 10 and decoder 9. The address signals are in the form of a 9 bit code read from a 10 bit location, the additional bit normally being zero. When a mode change is to be effected a "1" bit will be found in this location indicating that the currently processed channel is to be coupled to the central processor for signalling purposes. This "1" bit opens gates 15 in the interhighway splitting it into portions 5a and 5b, connects the clock signal generator 10 to decoder 8 via a gate 14 so that the contents of the speech store SS are read out cyclically, couples the output of this store and the output of the store 1 (the 9 bit code of which may have any significance) to the common control and connects the common control via a gate 17 to the other portion 5b of the interhighway. The common control can now process the received data and return the results or acknowledgement signals over interhighway portion 5b. Connections can also be made to multi-frequency receivers, service observation positions, exchange test desks, tones, announcements &c.