Testing and control system for supervisory circuits in electronic telephone exchanges

Claim 1

A TESTING AND CONTROL CIRCUIT FOR ELECTRONIC TELEPHONE EXCHANGE APPARATUS INCLUDING TWO DUPLICATE SUPERVISORY CIRCUIT AND COMPRISING, MEANS FOR SIMULTANEOUSLY COMPARING THE OUTPUT SIGNAL FROM ONE SUPERVISORY CIRCUIT WITH THE SIGNAL FROM THE OTHER SUPERVISORY CIRCUIT INCLUDING MEANS FOR DETECTING A STATE OF NON-CORRESPONDENCE BETWEEN SAID OUTPUT SIGNALS AND FOR PRODUCING A CONTROL SIGNAL IN RESPONSE THERETO, MEANS RESPONSIVE TO SAID CONTROL SIGNAL FOR INHIBITING THE OUTPUT OF ONE OF SAID SUPERVISORY CIRCUITS SO AS TO CAUSE OUTPUT SIGNALS TO BE SUPPLIED TO OTHER PARTS OF THE EXCHANGE APPARATUS FROM THE OTHER SUPERVISORY CIRCUIT ONLY, TESTING MEANS RESPONSIVE TO SAID CONTROL SIGNAL FOR FEEDING A SEQUENCE OF TEST SIGNALS AUTOMATICALLY TO THE SUPERVISORY CIRCUITS IN SUCCESSION FOLLOWING DETECTION OF SAID STATE OF NON-CORRESPONDENCE, MEANS FOR DETECTING DEPARTURES IN THE RESULTING OUTPUT SIGNALS OF SAID SUPERVISORY CIRCUITS FROM THE UNKNOWN CORRECT OUTPUT SIGNALS WHICH SHOULD RESULT FROM SUCH TEST SIGNALS, AND MEANS RESPONSIVE TO SAID MEANS FOR DETECTING DEPARTURES IN SAID RESULTING OUTPUT SIGNALS FOR REPLACING THE SAID ONE SUPERVISORY CIRCUIT SUPPLYING OUTPUT SIGNALS TO OTHER PARTS OF THE EXCHANGE APPARATUS BY THE OTHER SUPERVISORY CIRCUIT IF A DEPARTURE IS DETECTED IN TESTING THE SAID ONE CIRCUIT.