The EM is a low voltage photocell used for controlling exterior lighting. It works with Watt Stopper power packs and lighting control panels (Lighting Integrator and LP series panels) by signalling a change in light levels to the panel.

WATT STOPPER EM-24A2 1.89 INCH W X 1.57 INCH D X 2.64 INCH H SIZE; LIGHTING CONTROL PANEL POWER PACK APPLICATION; 24 VAC/VDC VOLTAGE RATING; EXTERIOR/ROOF MOUNTING; (4) #18 AWG WIRE TERMINAL TYPE; 15 FC TURN OFF LIGHT LEVEL; 1 FC TURN ON LIGHT LEVEL; POWER RATING 1 VA 1.57 INCH D X 2.64 INCH H SIZE; LIGHTING CONTROL PANEL POWER PACK APPLICATION; 24 VAC/VDC VOLTAGE RATING; EXTERIOR/ROOF MOUNTING; (4) #18 AWG WIRE TERMINAL TYPE; 15 FC TURN OFF LIGHT LEVEL; 1 FC TURN ON LIGHT LEVEL; POWER RATING 1 VA