System for the simultaneous coding of a number of television signals and for decoding thereof in radiofrequency

摘要

A system for the simultaneous coding of a number of television signals and for decoding thereof in radiofrequency. The radiofrequency TV signal or signals to be distributed undergo remodulation on at least one channel by a signal which does not alter the synchronism pedestal and which varies in accordance with an established sequence resident in the memory of the coder, offering differentiated application to each individual channel or to the whole range thereof. A data channel is also installed to include a channel identification code, an algorithmic code and a synchronisation code, these being the determinants for interpretation of the codes by a decoder at the subscriber's terminal and for application of a process of remodulation which is identical, synchronous and inverse in form to that of the coder in order to restore the original signal. It is of application in the protection of subscriber TV channels.