Reducing the power consumption of loads fed by one or more power supplies is achieved by the use of apparatus which determines the power supply output and, upon the occurrence of a predetermined condition, generates a signal to the power-consuming loads. In response to this signal, the loads alter their mode of operation so as to reduce the overall demand on the power supply. Several implementations of this load-shedding technique, which is particularly suitable for use in a communications system, are disclosed.

A system and method of limiting power consumption in a telecommunications equipment coupled between a plurality of far end subscriber lines and a plurality of near end subscriber lines are provided. The method includes monitoring and determining a number of ringing subscriber lines, comparing the number of ringing subscriber lines to a predetermined ringing threshold, monitoring and determining a number of off-hook subscriber lines, comparing the number of off-hook subscriber lines to a predetermined off-hook threshold, and blocking further ringing and/or off-hook subscriber lines in response to the number of ringing and/or off-hook subscriber lines reaching or exceeding the respective predetermined ringing and off-hook thresholds.

A digitizer tablet computer has a host processor connected to a service processor which, in turn, is connected to a digitizer controller and to a power subsystem microcontroller. A battery supplies the primary power for operating the computer but the computer is also connectable to an external source of DC power to charge the battery and to operate the computer when it is not running on battery power. The service processor includes a battery gauge the contents of which indicate how much power is left in the battery and how much time remains at the current rate of power consumption before the power runs out. The amount of remaining power in the gauge is determined by keeping track of power consumed, power added, and power lost during off periods. The use of the second derivative of a voltage versus time discharge curve creates a point from which relative accurate estimates can be made of how much longer the computer can be operated.

Various embodiments of an automatic alarm and communications processing system/method are presented. The alarm processing system/method monitors at least one sensor unit which is designed to provide an alarm signal upon occurrence of a corresponding predefined condition. An alarm signal is received at a central unit and a predefined alarm message is retrieved from memory based thereon. A selected telecommunications medium is then designated from at least two telecommunications medium coupled to the alarm processing system, and the retrieved predefined alarm message is automatically sent over the selected telecommunications medium. Preferably, the alarm processing system is powered down until an alarm signal is received at the central unit. Upon receipt of the alarm signal, powering of the alarm processing system is triggered, and subsequent to transmission of a predefined alarm message, powering of the alarm processing system is automatically removed. A detachable external programmer couples to and powers the central unit for custom programming of response parameters.

The disclosed system reduces power use during peak loads by automatically shifting the energization of the water heater to periods of off-peak power use. An energy controller maintains a calendar clock and controls the application of power to an electric water heater so that only on non-holiday weekdays, power to the water heater is interrupted during those periods of the day which have been predetermined to be the periods of peak power usage. The consumer whose water heater is controlled in accordance with the system is provided with an override button so that once a day the consumer may institute an override period to energize his water heater regardless of the peak power usage schedule. The energy controller contains in a microprocessor memory status data which includes the calendar time, a listing of the holidays, the schedule of peak power usage and the override interval. The energy controller is connected to an external module mounted outside the dwelling enclosure and by which a portable programming unit may be interconnected to the energy controller. By means of the portable programming unit, the accuracy of the status data can be verified or can be amended.