VIDEO，POWER，AND_CHANNEL_SELECT_SIGNAL_CARRIER

Published:2009/6/22 23:01:00 Author:Jessie | From:SeekIC

In the video system of Figs. A and B, a single coaxial cable carries power to the remote location, selects one of eight video channels, and returns the selected signal. The system can choose one of several remote surveillance-camera signals, for example, and display the picture on a monitor near the interface box. The heart of the multiplexer box (A) is a combination 8-channel rnultiplexer and amplifier (ICl). C11 couples the multiplexer's baseband video output to the coax, and L1 decouples the video from dc power arriving on the same line. This power-approximately 30 mA at 10 V-supplies all circuitry in the multiplexer box. In interface box (B), a desired channel is encoded by three bits, set either by switches as shown or by an applied digital input. Momentary depression of the send button triggers clownconverter IC1 and gated oscillator IC2A to initiate a channel-selection burst.



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