using intercom for remote control

using intercom for remote control
A 1A2 "dial-selective" intercom works by sending a short voltage pulse to a specific phone after a one- or two-digit number is dialed. Normally that voltage is used to activate a buzzer so someone at another phone knows to pick up the handset and press the intercom button to have a conversation.

That same voltage pulse can be used for a variety of remote control functions by directing the voltage at a "latching relay."

Latching relays are available for use on 12 volts AC, but they work fine with the 10 volts normally used for intercom buzzers. I previously used General Electric latching relays, but apparently GE no longer makes them, so find another brand.

A latching relay is unusual in that it has a mechanical "latch" feature that can keep its switching contacts connected ("on") even after the triggering voltage has been removed.

A second voltage pulse (delivered after dialing the number a second time) moves the switching contacts to the alternate position ("off").

Almost anything that can be controlled electrically can be controlled with this setup. I've used it for stereo systems, TVs, and even an electric waterfall that fed a swimming pool.