Moonlight

I' m having a problem with the COR out on the RT97s to COR in on the ID-O-Matic (latest version). The repeater trips the controller OK but the controller produces a voltage that back feeds into the RT97s COR circuit causing problems. One of the problems is a loud white noise being transmitted. Sounds like an open squelch. Disconnecting them and manually tripping the controller and the problem goes away. Courtesy beep works as it should and the loud white noise vanishes that the repeater was broadcasting. It appears some kind of isolation circuit is required like a reed relay or maybe a MOSFET. Anybody run into this problem? What was your solution? The COR on the RT97s goes low on carrier detect. The controller is expecting it's COR input to go low on trigger. When they are connected as expected the problem appears. Putting a meter on the line I see the voltage at about 2 volt on the COR line Then on key up there is a very brief drop like a pulse in voltage before coming back up to the 2 volts. It should stay low as long as its being keyed. Any ideas on a MOSFET isolation circuit? Any ideas would be much appreciated. Thanks in advance, WRYL353