These go inside the cabinet and switch on the signal indications by -24v, + ground. I opened some to show the insides. The small cube in upper right is a switching module from one like the top left, it contains 3 (RYG).
Anyone know if they once used relays in these load switches?
I could have sworn I heard a cabinet click when the indications changed but I'm pretty sure that cabinet didn't have an electromechanical controller.
Mechanical relays or optical are used. Both have about the same life, 100 million cycles. The relays tend to wear out either from contact wear or from the actual contacts or core breaking up from fatigue, generally failing open circuit. The electronic ones though tend to fail as a short circuit, especially if the output is shorted and the fuse is the wrong type or value, or the breaker fitted is slow. Typically you always have a relay contact to allow the conflict monitor to override the controller and switch the outputs off and switch in a flashing signal to the appropriate lights.
The clicking sound may be from a detector. Some of the older load switches have reed relays to isolate the 120v from the 24v controller. Newer load switches have a "Zero-Crossing" circuit to star the ON cycle when the sine wave is at zero volts, helps extend incandescent bulb life.
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Anyone know if they once used relays in these load switches?
I could have sworn I heard a cabinet click when the indications changed but I'm pretty sure that cabinet didn't have an electromechanical controller.