Tone control circuits

Claim 1

A TONE CONTROL CIRCUIT FOR USE IN A COMMUNICATION RECEIVER INCLUDING AN INPUT CIRCUIT ADAPTED TO HAVE BOTH A CONTROL TONE AND NOISE THEREIN AND A FUNCTION CIRCUIT TO BE CONTROLLED IN RESPONSE TO THE PRESENCE OF THE CONTROL TONE IN THE INPUT CIRCUIT, SAID CONTROL CIRCUIT COMPRISING A NOISE CHANNEL HAVING AN INPUT TERMINAL ADAPTED TO BE CONNECTED TO THE ASSOCIATED INPUT CIRCUIT AND AN OUTPUT TERMINAL, A TONE CHANNEL HAVING AN INPUT TERMINAL ADAPTED TO BE CONNECTED TO THE ASSOCIATED INPUT CIRCUIT AND AN OUTPUT TERMINAL, AN OUTPUT NETWORK HAVING FIRST AND SECOND INPUT TERMINALS RESPECTIVELY CONNECTED TO THE OUTPUT TERMINALS OF SAID CHANNELS AND AN OUTPUT TERMINAL ADAPTED TO BE CONNECTED TO THE ASSOCIATED FUNCTION CIRCUIT TO BE CONTROLLED, SAID OUTPUT NETWORK INCLUDING TWO RECTIFIERS HAVING ONE PAIR OF THE LIKE TERMINALS THEREOF CONNECTED TO EACH OTHER AND TO A POINT IN SAID OUTPUT NETWORK THAT CAN FLUCTUATE WITH RESPECT TO GROUND POTENTIAL, THE FIRST INPUT TERMINAL OF SAID OUTPUT NETWORK BEING CONNECTED TO ONE OF THE TERMINALS OF ONE OF SAID RECTIFIERS, THE OTHER TERMINAL OF THE OTHER OF SAID RECTIFIERS BEING CONNECTED TO SAID SECOND INPUT TERMINAL OF SAID OUTPUT NETWORK, SAID NOISE CHANNEL BEING OPERATIVE WHEN NOISE IS PRESENT IN THE INPUT CIRCUIT TO PROVIDE AN INPUT TO SAID OUTPUT NETWORK THAT CAUSES OPERATION OF SAID OUTPUT NETWORK TO PROVIDE A FIRST OUTPUT VOLTAGE THEREFROM HAVING AN AMPLITUDE PROPORTIONAL TO THE OUTPUT OF SAID NOISE CHANNEL AND TENDING TO INCREASE IN A FIRST SENSE WHEN THE INPUT TO SAID NOISE CHANNEL IS INCREASED WHEREBY IT IS EFFECTIVE TO CONTROL THE FUNCTION CIRCUIT IN A FIRST MANNER, SAID TONE CHANNEL BEING OPERATIVE WHEN THE CONTROL TONE IS PRESENT IN THE INPUT CIRCUIT TO PROVIDE AN INPUT TO SAID OUTPUT NETWORK THAT CAUSES OPERATION OF SAID OUTPUT NETWORK TO PROVIDE A SECOND OUTPUT VOLTAGE THEREFROM HAVING AN AMPLITUDE PROPORTIONAL TO THE OUTPUT OF SAID TONE CHANNEL AND TENDING TO INCREASE IN A SECOND SENSE OPPOSITE TO SAID FIRST SENSE WHEN THE INPUT TO SAID TONE CHANNEL IS INCREASED WHEREBY IT IS EFFECTIVE TO CONTROL THE FUNCTION CIRCUIT IN A SECOND MANNER.