Television receiver including a circuit arrangement for demodulating an NTSC-coded color signal

Claim 1

A color television signal receiver including a circuit arrangement for demodulating an NTSC-encoded chrominance signal available as a sequence of digital values, including an oscillator circuit (33) producing two reference signals of a chrominance subcarrier frequency and said reference signals being different in phase relative to each other, the oscillator circuit comprising an accumulator (16) which produces an output signal, said accumulator incorporating a register (18) coupled at its output to an output (21) of said accumulator and a first modulo-adder (17) coupled at its input to an input of said accumulator and coupled at its output to an input of said register and a waveform converter (31) which forms the reference signals from the accumulator output signal, and a phase comparator circuit (12) determining the phase of the reference signals and receiving during the occurrence of a color synchronizing signal in said NTSC-encoded chrominance signal, a signal produced in at least one demodulator (2) multiplying the chrominance signal by at least one of said reference signals, characterized in that in a first switching position of a change-over switch (23) an adjustable value is added in a second adder (26, 38) to the accumulator output signal and an output signal of the adder is applied to the waveform converter (31) and that the change-over switch (23) is in a second switching position during the occurrence of the color synchronizing signal, in said second position the accumulator output signal is applied to the waveform converter.