The methods used to scramble the picture is to alter the amplitude of the sync pulse or cause it to be omitted entirely from the video signal. Occasionally the sync pulse amplitude may be caused to vary at different times. In order to view the scrambled picture, the sync pulse must be reconstructed to its original amplitude. Some descrambleing techniques utilize a key of some type to reference and thereby restore the pulse to its original level. This key or pilot signal can be an audio sub carrier of some frequency that is a ratio of the horizontal sync frequency of 15.734 KHz.
Some systems have a digital signal that activates the decoder.
Other methods are the pilot less where horizontal pulses are attached to the vertical sync which will lock the horizontal frequency oscillator and reproduce the sync pulses. All these methods thus far regenerate the horizontal sync pulse by means of other timing signals. The universal descrambler doesn't use any of the methods discussed to regenerate the sync pulses. This signal is the key for regenerating all other timing signals to produce a clear picture. If you decide to build one of these units and need help please email me.