Automatic color saturation control responsive to ambient light level

Claim 1

A colour television receiver having a picture tube with a screen; a chrominance signal channel for translatiNg a chrominance signal received by said receiver, said chrominance signal channel including chrominance signal amplifying means having an output terminal and chrominance signal demodulating means; an automatic saturation control system, said automatic saturation control system comprising an A.G.C. system including detecting means for detecting a part of the chrominance signal translated by said chrominance signal channel prior to demodulation thereof to provide a D.C. signal that varies in magnitude responsive to changes in the level of the chrominance signal, means for applying said D.C. signal to said chrominance signal amplifying means to maintain the level of the chrominance signal at said output terminal of said chrominance signal amplifying means substantially constant, a saturation threshold control circuit comprising a radiation-sensitive device, and means connecting said device in circuit with said A.G.C. system to vary the level of the chrominance signal regulated by said A.G.C. system in response to changes in radiation incident on said device and to which said device is sensitive to increase said level in response to an increase in radiation and to decrease said level in response to a decrease in radiation.