Relays
Some of the earliest circuit breakers were current sensors that
drove relays to interrupt the current flow to the track. The
sensing circuitry was pretty rudimentary on some versions,
resulting in some rather spectacular sparks and the resulting
wheel pitting.
The Digitrax PM42 four-section circuit breaker or auto-reverser
[3] was one of the first electronic units to achieve wide usage.
As low-on-resistance transistors have become more available
and less expensive, the relay-style circuit breakers have tended
to fade away. Given today’s technology, I would eschew relay
breakers on a new layout and suggest upgrading to fully elec-
tronic units on older layouts.
