The Burst Electronics Model VSA detects the presence of composite video at its A input and outputs this video. If loss of video on the A input is detected, then the unit switches to the B input, lights a Red LED, and energizes an internal "tally" relay. This relay may be used to control external devices. The tally relay has both normally closed and normally open contacts (Form C relay). This Model includes stereo audio switching, audio follow video. The video detection process utilizes a sophisticated...