Abstract: A switching arrangement for selecting one of a number of video signals. The circuit includes a switch unit preferably in integrated circuit form of pairs of synchronously operated switches for selecting video signal from a particular one of the video sources. A first switch of each pair is coupled to a respective video source for selectively providing a video signal to a common output when conductive. To provide sufficient isolation at video frequencies, the second switch of each switch pair is coupled between a reference potential and a respective one of a plurality of signal inhibiting stages for providing a control signal to the signal inhibiting stage dependent upon its conductive state.

Abstract: 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.