Black and white and colour TV transmission system - can be coded by PAL or NTSC system

摘要

Additional two-channel sound signals are transmitted in horizontal blanking periods and scanned at twice the line frequency. They are transmitted in digital form during back porch extended by shortening of the synchronisation signal. Pulses have a repetition frequency of the colour carrier, and its phase is equal to that of the latter. Colour synchronisation signal for decoding is recovered by evaluation in the receiver of the sound signals, using the same clock pulses in sender and receiver. A control derives these pulses from the sound signal pulse repetition frequency. The control unit has a counter for the pulses and divides each line period into four equal sections. A logic network delivers clock pulses necessary for each scanned value processing.