SELC Photocell Controller Light Switch Timer 841 Model 841077 NEMA Dusk to Dawn is a product manufactured by Solar Enterprise Lighting Controls (SELC) Ltd. It is a type 841 model with a manufacturer part number of Type 841. This product is a photocell controller that automatically switches lights on and off based on the ambient light levels. It also has a timer function and is designed to operate from dusk to dawn.