Abstract: An external power-management device controls the supply of electric power from a wall outlet to a refrigerated vending machine. The system includes a switch that couples power in an ON condition and decouples in an OFF condition. The switch is controlled by a controller based on data received from a current sensor, an occupancy sensor, a temperature sensor, and a time-of-year circuit. Upon startup, the current is monitored to determine maxima and minima for the vending machine. The system supplies power to the appliance during business hours as indicated by the time-of-year circuit and while the vicinity is occupied as determined by the occupancy sensor irrespective of the values for current and temperature. Absent the current sensor, the power would be decoupled after a predetermined duration of non-occupancy during nonbusiness hours.

Abstract: A power conservation system (PCS) includes a data handler, a controller and a power switch. The data handler is located between a host network and a network printer, while the power switch is between an AC power source and the printer's power input. The PCS can thus shut down the printer during periods when no data is being sent to the printer. The PCS monitors data to and from the printer, allowing it to track the printer's state and to capture its network identification. State tracking permits the PCS to emulate the printer when it is down and when it is booting. Additionally, the information stored in a state memory of the data handler can permit the printer's last ready state to be reconstructed after it turns on and boots to a ready state. In some cases, the data handler can answer network requests without turning on the printer. Thus, the PCS provides for effective power conservation while remaining invisible to a user.

Abstract: A method and circuit for reverse phase control of alternating current being delivered to a load are disclosed wherein voltage-controlled semiconductor switches, such as MOSFET's and IGBT's, are used as electronic switches to conduct voltage during the leading edge of the AC voltage cycle and conduction is terminated when the desired phase angle of the current flow has been reached. The disclosed method and circuit eliminate the need for zero crossing detection of the AC waveform and ensure that the voltage-controlled switches are always turned on before the zero crossing thereby minimizing radiated interference and incandescent lamp hum. The method used is primarily digital in nature making mechanical input or electronic input for the power control equally efficient to implement.