Burst Electronics VDS-3 - Manual (Page 2)

1 Video Detector
Video Detector Switch
Description:
The Burst Electronics Model VDS (and the VDS-3, a 3 channel
version) 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 (VDS only)
and energizes an internal “tally” relay (standard on VDS and VSA,
optional on VDS-3). This relay may be used to control external
devices. The tally relay has both normally closed and normally
open contacts (Form C relay). The Model VSA includes stereo
audio switching, audio follow video.
The video detection process utilizes a sophisticated sync separa-
tor circuit and a micro controller IC to analyze the A input. The
composite sync tip amplitude, vertical sync, horizontal sync, and
frame pulse are all analyzed by the micro controller to determine
the quality of the incoming video on the A input.
Setting the DIP Switch:
The DIP switch sets the video accept/reject criteria. To set the
switch, remove the cover. There is a four position DIP switch on
the board that sets the loss of video software options and a pot that
adjusts the sync tip reject point. The switch is factory preset to Up,
Up, Up, Down. The sync amplitude is set to -20 IRE trip point.