video operated relay is designed to key a small 12v relay when
horizontal sync is sensed at its input. It can be used in a variety of
applications, for example, to remotely activate a video recorder, in an
ATV repeater system or as a receiver warning alarm. Should it be
necessary to activate a heavy relay, say for transmitter power
applications, the small relay may be used to switch in a large one.
frequency of the decoder should be set by using a frequency counter
connected to the test point and carefully adjusting the pot to within
100Hz of 15625Hz. This should be done with no video connected. The
normal lock-in range is around plus and minus 800Hz to allow for odd
computer horizontal frequencies or badly adjusted cameras.
circuit appeared in A5 Amateur TV magazine for August 1984 and thanks
are due to the author and publisher for permission to reproduce it here.
The design is from P.C.Electronics of 2522 Paxson Lane, Arcadia,
CA91006, USA who produce a printed board or assembled module.