Gte Sylvania Incorporated

Gte Products Corporation

Douglas W Constable

Robert C Wheeler

John D Lovely

Kenneth J Burdick

In a VIR-responsive television receiver that also includes a manually-operated tint preference control, a circuit for indicating correct setting of that control. A comparator detects approximate equality between the VIR tint control voltage and the tint preference voltage. An LED, driven by the comparator, indicates the existence of this condition.

Correct tint indicator circuit for a VIR system

A circuit utilizing a single clamp, and therefore requiring only a single bias supply, to DC clamp the inputs of the three chrominance amplifiers is shown. The clamp employs a switch that is connected to the bias supply and coupled by separate diodes to the inputs of the chrominance amplifiers. The switch and diodes are conductive only during the horizontal retrace period. As a result, during the retrace period, the amplifier inputs are clamped to a DC value determined by the bias supply; during the trace, or information-bearing period the inputs are isolated from the supply, as well as from each other.

Clamp circuit for RGB output stages

A DC controlled amplifier is used to control the chrominance gain, and hence the color saturation, of a television receiver. The voltage on the wiper of a Color Control variable resistor and the output of an Automatic Color Level (ACL) detector are combined in a summing network to provide a DC voltage to the controlled amplifier. The ACL detector develops an output voltage that tends to maintain the peak-to-peak chrominance signal, and therefore the color saturation, at or below a threshold level. A control tracking circuit varies the threshold level in accordance with the voltage on the wiper of the color control variable resistor, thereby maintaining the dynamic range of the Automatic Color Level Control System relatively independent of the setting of the Color Control.

Automatic color level control system with threshold tracking

Contrast and color levels in a color television receiver are automatically varied with ambient light variations by an RC circuit AC coupling an ambient light responsive device to a luminance signal channel and DC coupling the ambient light responsive device to a DC potential source and a chrominance signal channel.

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Batavia, NY, United States of America

Douglas W Constable