Magnetic recording apparatus with selective recording of auxiliary audio signal

An apparatus for recording a television signal which includes a video signal, a main audio program and may include a Second Audio Program (SAP), comprising:

• a tuner and intermediate frequency circuit for receiving said television signal and generating a processed video signal therefrom;
• a first frequency demodulator for producing a sum audio signal including a sum of left and right stereo channels;
• a second frequency demodulator, receiving said sum audio signal, for producing a difference audio signal including a difference of left and right stereo channels;
• matrix means for producing a matrix signal indicative of the presence of said difference audio signal;
• an SAP demodulator, also receiving said sum audio signal, for demodulating an SAP audio signal, and for determining if said television signal includes an SAP audio signal, said SAP demodulator producing a signal indicative of the presence of said SAP signal;
• control means responsive to said signal indicative of the presence of said SAP audio signal and responsive to an input signal indicating whether said SAP audio signal is to be recorded, for producing a control signal;
• a first frequency modulator for selectively modulating either said SAP audio signal or said sum audio signal to produced a first modulated audio output signal;
• a second frequency modulator for modulating said difference audio signal to produced a second modulated audio output signal;
• gating means, responsive to said control signal and said matrix signal for enabling operation of said second frequency modulator only when said difference audio signal is present;
• switching means, responsive to said control signal, for selectively switching either said SAP audio signal or said sum audio signal to said first modulator, and said difference audio signal to said second frequency modulator;
• combining means for combining said processed video signal with said first and second modulated audio output signals to produce a combined signal;
• a PCM processor receiving said sum and difference audio signals for encoding with pulse code modulation;
• and
• recording means including a magnetic recording head, for recording said pulse code modulated signal on a magnetic recording medium.