Subscription television system having keyed generation of sync signals at the receiver

Claim 1

IN A TELEVISION RECEIVED, IN COMBINATION, RECEIVING MEANS FOR RECEIVING AND REPRODUCING A VIDEO SIGNAL AND A KEY SIGNAL OF SUBSTANTIALLY SINUSOIDAL WAVESHAPE, SAID RECEIVING MEANS INCLUDING PICTURE DETECTING MEANS FOR DERIVING THE PICTURE SIGNAL FROM A RECEIVED VIDEO SIGNAL, MEANS CONNECTED TO SAID PICTURE DETECTING MEANS FOR REPRODUCING A PICTURE FROM THE OUTPUT OF SAID PICTURE DETECTING MEANS, SYNCHRONIZING AND SCANNING MEANS CONNECTED TO SAID PICTURE REPRODUCING MEANS, AND RECEIVER AUDIO MEANS FOR RECEIVING AND REPRODUCING AN AUDIO SIGNAL IN SYNCHRONISM WITH SAID VIDEO SIGNAL, SAID RECEIVER AUDIO MEANS COMPRISING AUDIO DETECTING MEANS FOR DERIVING SAID AUDIO SIGNAL FROM THE RECEIVED SIGNAL AND MEANS FOR REPRODUCING SAID AUDIO SIGNAL FROM THE OUTPUT OF SAID AUDIO DETECTING MEANS; AND DECODING MEANS FOR PRODUCING HIROZONTAL SYNCHRONIZING SIGNALS FROM THE RECEIVED KEY SIGNAL SO AS TO PROVIDE IN SAID RECEIVER A VIDEO SIGNAL INCLUDING SAID HORIZONTAL SYNCHRONIZING SIGNALS, SAID DECODING MEANS HAVING AN INPUT CONNECTED TO A COMMON POINT BETWEEN SAID AUDIO DETECTING MEANS AND SAID AUDIO SIGNAL REPRODUCING MEANS AND AN OUTPUT CONNECTED TO SAID PICTURE DETECTING MEANS AND COMPRISING FIRST PHASE SHIFTING AND PULSE FORMING MEANS FOR CONVERTING SAID SUBSTANTIALLY SINUSOIDAL KEY SIGNAL INTO A FIRST SERIES OF SUBSTANTIALLY SHARP PULSES, FIRST PULSE SHAPING MEANS FOR CONVERTING SAID FIRST SERIES OF SUBSTANTIALLY SHARP PULSES INTO A FIRST SERIES OF SUBSTANTIALLY SQUARE PULSES, SECOND PHASE SHIFTING AND PULSE FORMING MEANS FOR CONVERTING SAID SUBSTANTIALLY SINUSOIDAL KEY SIGNAL INTO A SECOND SERIES OF SUBSTANTIALLY SHARP PULSES, SECOND PULSE SHAPING MEANS FOR CONVERTING SAID SECOND SERIES OF SUBSTANTAILLY SHARP PULSES INTO A SECOND SERIES OF SUBSTANTIALLY SQUARE PULSES, AND MIXING MEANS FOR COMBINING SAID FIRST AND SECOND SERIES OF SUBSTANTIALLY SQUARE PULSES TO PROVIDE A RESULTANT SERIES OF HORIZONTAL SYNCHRONIZING PULSES.