Greetings:
I would appreciate any information concerning the Master Lock Ultrasonic alarm controller system (model 2428 is an example), especially a description of the power line signalling method and available devices when this product was sold.
The 2428 unit we have has a transmitter connected only to the power line through the N.O. contacts on the alarm relay which employs a neon-bulb relaxation oscillator to key the RF at 1HZ when activated. The transmitter board contains a few transistors, discretes, a slug-tuned coil and a yellow dime-sized part labeled "channel 4", perhaps a resonator?
The ultrasonic alarm pcb has four 1458 op-amps, two relays and discretes; date codes ~1977
Regards,
Michael