Abstract: A photocell unit in combination with a programmed microprocessor which samples the output of the photocell and detects day or night by sampling over a predetermined period of time, e.g. 80 minutes to establish a right reference value and a predetermined number of samples of increasing light values to establish a "sunrise detect value" to turn lights off. A further predetermined increase in light values is used to establish a "sunset detect" light value. This value is retained throughout the day until sensed light values again diminish to the "sunset. The sampling techniques makes the system immune from errors due to transient lights and also avoid unwanted daylight operation of lights or undetected light outages.

Abstract: A system is disclosed for sensing selected conditions particularly adjacent to an unoccupied commercial business building and taking the appropriate action. Corrective action may include shutting down a system, sending a signal to an occupied location for evaluation of the selected abnormal condition, or making a record of the abnormal condition for rectification at a later time. The system includes one or more light level sensors including microcomputer controlled photocell units directed to observe the light level at selected locations and to transmit signals indicating sensed light values below a desired value, and includes a receiver receiving the transmitted signals and which responds to such signals to produce a correction signal. If the commercial establishment is a bank and the light level is at an ATM (automatic teller machine) the system may respond to the correction signal by temporarily shutting the ATM machine down and illuminating a sign to indicate that the ATM is not open.