Colour television receivers

Claim 1

IN A COLOUR TELEVISION RECEIVER COMPRISING MEANS FOR RECEIVING COLOUR TELEVISION SIGNALS; MEANS FOR DERIVING FROM SAID COLOUR TELEVISION SIGNALS A SEQUENTIAL SIGNAL ALTERNATELY BUILT UP BY A FIRST AND A SECOND COLOUR INFORMATION SIGNAL ALTERNATING AT THE LINE FREQUENCY, SAID SEQUENTIAL SIGNAL BEING SUCH THAT THE SUM OF, AND THE DIFFERENCE BETWEEN, SAID SEQUENTIAL SIGNAL AND A DELAYED SIGNAL DERIVED FROM SAID SEQUENTIAL SIGNAL THROUGH DELAYING IT BY A DURATION EQUAL TO A LINE PERIOD, RESPECTIVELY BUILD UP A THIRD AND A FOURTH COLOUR INFORMATION SIGNAL; AND MEANS FOR DERIVING FROM AN AUXILIARY SIGNAL INCLUDED, AT RECURRENT TIME INTERVALS IN SAID COLOUR TELEVISION SIGNALS, A SWITCHING SIGNAL HAVING A FIRST LEVEL OR A SECOND LEVEL ACCORDING TO WHETHER SAID FIRST OR SECOND COLOUR INFORMATION SIGNAL IS PRESENT IN SAID SEQUENTIAL SIGNAL: A COLOUR TELEVISION RECEIVER CIRCUIT FOR DERIVING FROM SAID SEQUENTIAL SIGNAL TWO SIMULTANEOUS AND SEPARATE COLOUR INFORMATION SIGNALS, SAID RECEIVER CIRCUIT COMPRISING: A FIRST INPUT; MEANS FOR APPLYING SAID SEQUENTIAL SIGNAL TO SAID FIRST INPUT; A DIRECT CHANNEL AND A DELAY CHANNEL HAVING RESPECTIVE INPUTS COUPLED TO SAID FIRST INPUT, AND RESPECTIVE OUTPUTS; SAID DELAY CHANNEL COMPRISING A DELAY DEVICE FOR DELAYING THE SIGNAL PROPAGATING THERETHROUGH BY A DURATION EQUAL TO A LINE PERIOD, RELATIVELY TO THE SIGNAL PROPAGATING THROUGH SAID DIRECT CHANNEL; AN ADDING DEVICE HAVING TWO INPUTS, RESPECTIVELY COUPLED TO SAID OUTPUTS OF SAID DIRECT AND DELAY CHANNELS, AND AN OUTPUT, FOR DELIVERING AN OUTPUT SIGNAL PROPORTIONAL TO THE SUM OF ITS TWO INPUT SIGNALS; A SUBTRACTING CIRCUIT, HAVING A FIRST AND A SECOND INPUT RESPECTIVELY COUPLED TO SAID OUTPUTS OF SAID DIRECT AND DELAY CHANNELS; SAID SUBTRACTING CIRCUIT COMPRISING; FIRST MEANS FOR DELIVERING A FIRST DIFFERENCE SIGNAL WHICH IS EQUAL, TO WITHIN A CONSTANT FACTOR, TO THE SIGNAL APPLIED TO THE