Correct. Momentary switches. The 24V is rectified, so
a DC pulse is applied to one winding or the other of the relay.
The relay then latches magnetically and needs no more input power.
A switch anywhere else in the house can then cause the relay to
change state.

A nice application is a large property where outside lights
can be switched on/off from dozens of indoor locations.
Or, a bank of switches can control *any* light in the house from
one location!

The system *did* catch on and was quite popular.
But this was 40 years ago!!


I remember these. It was sort of like an X10 system with wires.

One big problem was maintenance. These were usually installed in a
home during the original construction. The relays were mounted in
electric box cutouts with the relay mechanism outside the box and
inaccessible behind the plasterboard.

If a relay went bad, it was almost impossible to replace it without
smashing a hole in the wall.

The switches also went bad, from time to time. They were really no
more than SPDT momentary doorbell buttons.

Beachcomber