Method and apparatus for detecting timing pulses for scrambled television system

An apparatus for detecting timing pulses for descrambling a scrambled intermediate frequency (IF) television signal having at least a video IF signal component, a sound IF signal component, and timing pulses amplitude modulated (AM) on said sound IF signal, the apparatus comprising:

• a first filter circuit for separating a video IF signal from a scrambled television IF signal through a descrambler circuit;
• a second filter circuit for separating a sound IF signal from the scrambled television IF signal;
• a PLL (phase-locked loop) circuit for generating a local oscillation signal having a video carrier frequency in synchrony with the separated video IF signal;
• a mixer circuit for outputting a beat signal by mixing the sound IF signal separated by the second filter circuit with the local oscillation signal generated by the PLL circuit;
• a third filter circuit for separating a main sound IF signal from the beat signal output by the mixer circuit;
• and
• an AM demodulator circuit for demodulating timing pulses from the main sound IF signal, whereby the timing pulse is fed to the descrambler circuit and thereby the scrambled television IF signal is descrambled.