Supervisory control system

Claim 1

IN A SUPERVISORY SYSTEM INCLUDING AT LEAST A FIRST AND A SECOND STATION COUPLED BY A PATH OVER WHICH SETS OF IMPULSE SIGNALS ARE TRANSMITTED AS A GROUP TO EFFECT A CONTROL OPERATION, SIGNAL TRANSMITTING MEANS AT EACH STATION FOR SENDING SAID SIGNALS INCLUDING MEANS FOR PREFIXING EACH GROUP OF IMPULSE SIGNAL SETS WITH A KEY CODE COMPRISED OF A PREDETERMINED NUMBER OF IMPULSES, TRANSIENT PROTECTION MEANS AT EACH STATION FOR CODING PREDETERMINED IMPULSES OF SAID KEY CODE OF A GROUP OF THE IMPULSE SIGNALS BY EFFECTING A PREDETERMINED VARIATION OF THE DURATION OF SAID PREDETERMINED KEY CODE IMPULSES RELATIVE TO THE OTHER IMPULSES IN THE KEY CODE, AND SIGNAL RESPONSIVE MEANS INCLUDING SAID TRANSIENT PROTECTION UNIT AT EACH STATION OPERATIVE RESPONSIVE TO THE RECEIPT OF A KEY CODE WITHOUT SAID PREDETERMINED CODED IMPULSES OF SAID PREDETERMINED VARIATION IN THE PROPER SEQUENCE TO GENERATE A RESET SIGNAL AND MEANS FOR COUPLING SAID RESET SIGNAL TO THE RESET EQUIPMENT FOR THE STATION TO BLOCK ACCESS THERETO FOR THE SYSTEM.