A lamp adaptor with a photoelectric circuit that energizes a light bulb at dusk and keeps the bulb energized for a number of hours previously selected by suddenly blocking the light sensing element for a corresponding number of seconds. As an aid in counting the number of seconds that the sensor is blocked,...http://www.google.se/patents/US6194847?utm_source=gb-gplus-sharePatent US6194847 - Photoelectric lamp control with timer adjustable by light blockage
