K4121C Photo Controls feature stem mounting, thermal-type, controls with single and multi-voltage models. Thermal-type photo controls provide dusk-to-dawn lighting control and a delay action, which eliminates loads switching OFF due to car headlights, and lighting. The thermal-type controls feature a cadmium sulfide photocell and a sonic-welded polycarbonate case and lens to seal out moisture. The design utilizes a dual temperature compensating bimetal and composite resistor for reliable long life operation over ambient temperature extremes. These models are California Title 24 compliant.