Acom 04AT Operating Manual page 45

mentioned above. During that time, the transceiver feeds continuous RF power. At
each step the controller first activates the sensors with a short pulse of RF power by
blocking the MOSFET for a short time, and in a few milliseconds reads out the status of
the sensors, then it blocks the power to the relays by saturating MOSFET again, and in
this manner switches the relays synchronously with the power and keeps the contacts
safely clean (S 5.1).
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Fig. 7-1 ACOM 04AT Block Diagram