Review on Federal Signal MSL3 120 MicroStat Indicator by Mark Loredo

The description states that this device is "PLC" compatible, indicating that the light fixture uses relays or solid state switches that are used to turn the light on and off with logic low signals can ). Instead, there are just three 120-volt lights connected in parallel with a common neutral and three hot leads (one for each bulb). It's no more "PLC capable" than a table lamp! Otherwise it's a pretty nice modular design, but if you're using it on a machine be prepared to add external relays or other circuitry to interface with your controller.