Dual modulated remote control system

Claim 1

A PRIVATE COMMUNICATION SYSTEM COMPRISING, A TRANSMITTER HAVING MEANS FOR RADIATING SIGNAL ENERGY AT A PREDETERMINED CARRIER FREQUENCY AND MODULATING MEANS FOR SEQUANTIALLY MODULATING SAID SIGNAL ENERGY AT LOWER AND HIGHER MODULATING FREQUENCIES, A RECEIVER HAVING MEANS FOR DETECTING SAID LOWER AND HIGHER MODULATING FREQUENCIES WHEN TUNED TO SAID PREDETERMINED CARRIER FREQUENCY, SEPARATE CHANNEL MEANS COUPLED TO SAID DETECTING MEANS FOR RESPECTIVELY CONDUCTING SIGNAL ENERGY AT THE LOWER AND HIGHER MODULATING FREQUENCIES, A UTILIZATION CIRCUIT HAVING RELAY MEANS RESPECTIVELY ENERGIZED BY MODULATED SIGNAL ENERGY AT SAID LOWER AND HIGHER MODULATING FREQUENCIES COMPLETE THE CIRCUIT, INTERLOCK MEANS COUPLED TO SAID SEPARATE CHANNEL MEANS FOR PREVENTING ENERGIZATION OF THE RELAY MEANS IN RESPONSE TO SIGNAL ENERGY SIMULTANEOUSLY CONDUCTED THROUGH THE CHANNEL MEANS AT SAID LOWER AND HIGHER MODULATING FREQUENCIES, AND DELAY MEANS RESPONSIVE TO ENERGIZATION OF THE RELAY MEANS BY SIGNAL ENERGY AT ONE OF SAID MODULATING FREQUENCIES FOR PROLONGING ENERGIZATION THEREOF TO OVERLAP RECEPTION OF MODULATED SIGNAL ENERGY AT THE OTHER MODULATING FREQUENCY.