Monophonic-stereophonic automatic switching and demodulator circuit

Claim 1

APPARATUS FOR SWITCHING A COMMON PAIR OF OUTPUT TERMINALS TO MONOPHONIC AND STEROPHONIC SIGNAL OUTPUTS, THAT COMPRISES, A TRIGGER CIRCUIT BIASED NORMALLY TO OPERATE IN ONE OF TWO STATES OF CONDUCTION, MONOPHONIC AND STEREOPHONIC SIGNAL-RECEIVING MEANS, A STEREOPHONIC-SIGNAL DEMODULATOR CIRCUIT COMPRISING A PLURALITY OF DETECTING MEANS BIASED SO THAT ONE OF THE SAID DETECTING MEANS IS NORMALLY EFFECTIVE, MEANS FOR CONNECTING THE MONOPHONIC AND STEREOPHONIC SIGNAL-RECEIVING MEANS TO THE DEMODULATOR CIRCUIT, MEANS OPERATIVE IN THE PRESENCE OF A MONOPHONIC SIGNAL FOR MAINTAINING THE TRIGGER CIRCUIT IN ITS SAID ONE STATE TO APPLY THE MONOPHONIC SIGNAL OUTPUT THROUGH THE SAID ONE DETECTING MEANS TO THE SAID OUTPUT TERMINALS AND TO RENDER THE DEMODULATOR CIRCUIT INEFFECTIVE TO DEMODULATE STEREOPHONIC SIGNALS, MEANS RESPONSIVE TO THE OUTPUT OF THE STEREOPHONIC SIGNAL-RECEIVING MEANS FOR MODIFYING THE BIAS OF THE SAID TRIGGER CIRCUIT TO CAUSE THE SAME TO ASSUME ITS OTHER STATE, MEANS CONTROLLED BY THE ASSUMPTION OF THE SAID OTHER STATE BY THE TRIGGER CIRCUIT FOR CHANGING THE DETECTING MEANS BIAS TO RENDER THE SAID ONE DETECTING MEANS INEFFECTIVE AND OTHER OF THE DETECTING MEANS EFFECTIVE WHILE RENDERING THE STEREOPHONIC DEMODULATOR CIRCUIT EFFECTIVE AND APPLYING THE STEREOPHONIC PAIR OF RECEIVED SIGNALS THROUGH THE SAID OTHER DETECTING MEANS TO THE PAIR OF SAID OUTPUT TERMINALS, THE SAID RESPONSIVE MEANS INCLUDING MEANS CONTROLLED BY A RECEIVED PILOT SIGNAL ACCOMPANYING THE STEREOPHONIC SIGNALS FOR PRODUCING A DIRECT-CURRENT BIAS-MODIFYING SIGNAL FOR APPLICATION TO THE SAID TRIGGER CIRCUIT, AND MEANS RESPONSIVE TO A NOISE SIGNAL INDICATIVE OF INADEQUATE STEREOPHONIC SIGNAL FOR ELIMINATING THE SAID DIRECT-CURRENT BIAS-MODIFYING SIGNAL, THEREBY RETURNING THE TRIGGER CIRCUIT TO ITS SAID ONE STATE OF CONDUCTION.