Intercom amps on TK-30s and TK-31s
 

Hi All. Does anyone here have any information on the Daven Model 90 headset amps that were installed on TK-30/10 and TK-31/11 cameras as an after-thought. I can't find any info on it or working circuits on the cameras that actually incorporated it from the get-go. I'd like to get mine working but have no schematics or reference in the RCA camera manuals.