BURST GATE KEYING AND BACK PORCH CLAMP PULSE GENERATOR

摘要

A pulse generator for a television receiver produces keying pulses during the video signal back porch interval in order to energize burst gate and brightness control circuitry. The pulse generator is triggered by horizontal sync pulses under strong/ noise-free video signal conditions. As the quality of the video signal and the horizontal sync pulses deteriorate due to noise or a weakening signal, the pulse generator is triggered by horizontal retrace pulse in order to provide keying pulses under all video signal conditions.