DB-1 is a doorbell. White wire is audio output, red is power. Green wire 'keys' the noise when it's grounded, and the missing wire is probably ground.
Connecting the green wire to the transmit pin of the mike socket makes it a key-up 'bong'. A switch in line with the green wire shuts it off.
The voltage on the green wire might make it unsafe for radios like RCI2950 clones, where the mike doesn't key the radio, but keys a 5-Volt computer chip. A check to see how much voltage appears on the green wire will probably prove to be more than 5 Volts. This can be toxic to the unobtainium CPU chip in those radios.
Best I can remember, anyway.
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