Telecommunications system, particularly a telephone exchange system, having overload protected sequential logic systems

Claim 1

A telecommunications system comprising: a plurality of lines and trunks, arranged in groups, for connection to subscriber stations and for carrying call information including initial switching identifiers as control signals followed by characters; a central information-processing system having a limited call-handling capability with respect to its information-processing capacity; a switching network connected to said central information processing system; a plurality of partially-centralized switching devices each connected to a respective line/trunk group and to said central information-processing system via said switching network, and each operable to receive, intermediately store and transmit call information to said central information-processing system for processing to set up calls between calling and called subscriber stations; traffic load measuring means connected to each of said partially-centralized switching devices and responsive to said initial switching identifiers to produce control signals representing said switching identifiers and therefore representing the information-processing traffic load; a plurality of cyclically-decremented counting means each connected to a respective partially-centralized switching device, each of said counting means incremented only by said control signals representing switching indentifiers and operable to produce and transmit an overload signal to the respective partially-centralized switching device upon reaching a predetermined count representing a traffic load limiting value to prevent acceptance of following characters when such characters have not yet been received and prevent the acceptance of further initial switching identifiers when such characters have already been received; and means connected to and operable to cyclically deincrement said counting means at uniform time intervals.