This versatile timer features convenient photocell activation and a temperature sensor mode ideal for use with block heaters. Photocell mode-executes programming when darkness threshold reached at dusk/dawn. Adjustable darkness threshold-lets user customize darkness level at which photocell mode activates programming. Temperature sensor mode-executes programming when temperature falls to -12°C/10°F. Rugged, weatherproof construction enables indoor or outdoor use. Temporary bypass-enables override without affecting programming.