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

Claim 1

A telecommunications systems comprising: a plurality of lines and trunks, arranged in groups, for connection to subscriber stations and for carrying call information; a central information-processing system having a limited call-handling capability with respect to its information-processing capacity; a central switching network connected to said central information-processing system; a plurality of partially-centralized switching devices each including a sub-switching matrix network connected to a respective line/trunk group and to said central switching network, and each including switch means operable to receive an intermediately store and transmit call information including line signals, selection identifiers, and line characters to said central information processing system for processing to set up calls between calling and called subscriber stations and for transmitting control signals including alternating current call pulses, audio signals, selection identifiers and line characters over said lines and trunks, and operable to set up incoming and outgoing connections over said central switching network so that a partially-centralized switching device is utilized at least once per through-connection event; and a plurality of counting means, each including a cyclically-deincremented counter, each counting means connected to a respective partially-centralized switching device and each of said counters incremented in response to seizure of the respective partially-decentralized switching device and operable to produce and transmit an overload signal to the respective switch means of the partially-centralized switching device upon reaching a predetermined count representing a traffic load limiting value to prevent further seizures thereof during the existence of the overload signal.