> I found it. It`s this thing:
That is the receive magnet. An electromagnet coil that is supposed to be
turned on an off by the incoming serial bits The complex camshaft arrangement
samples the state of that in the middle of every bit-time and effectively does
the serial to parallel conversion.
OK, it should be being fed by a DC current. There is a subchassis on the
call control unit wiht a 9 pin (I think) molex plug on the side. It contains
a plug-in PCB, a transformer and a capacitor. That's where you should
be looking. Perhaps the capacitor has dried up so there is excessive
ripple on the supply lines.