One downside was that the electrical relay contacts would get dirty and required constant cleaning.

I should be able to operate the relay contacts if I can find them.

They are used as high-current switches or contactors, where contact erosion from constant cycling would be a problem for conventional relay contacts.

Gersen traced the circuit, and with the point of his metal cusp shorted across the relay contacts.

They are used where contact erosion would be a problem for conventional relay contacts.

Circuits through the relay contacts therefore report whether or not the track is occupied.

One perspex case warped in the heat, and touched the relay contacts, holding them up.

Each relay contact was bridged by a resistor.

Memory circuits in the form of latches can also be created by having a relay contact complete the circuit of its own coil when operated.

Double switching does of course cost more wires, more relay contacts, and testing.