Abstract: A window operating system includes a motor control circuit for controlling the operation of direct current permanent magnet motors mounted on window operators associated with each window. Each of the motors on each of the windows is connected to the control circuit only by a pair of wires which both power the motor and provide information to the control circuit as to the status of motor operation. The status of motor operation is determined by monitoring the back electromagnetic force expressed by the motors. To help differentiate back electromagnetic force from supply voltage supplied to the motors, the motors are supplied with full rectified alternating current power, rather than simple direct current, so that the presence or absence of zero voltage between half waves of the voltage expressed across the motors can be monitored to determine the absence or presence of back electromotive force during those time periods.

Abstract: A signal monitoring device useful to monitor power consumption level employs a phase locked loop and an associated frequency reduction circuit to convert relatively low frequency input pulse signals to an output signal representative of power consumption.

Abstract: Incremental heating and cooling sources are energized and deenergized as required to meet the maximum heating and cooling demands of any of the zones in a temperature controlled space. Common references and comparators are employed for both heating and cooling controls.

Abstract: Incremental heating and cooling sources are energized and deenergized as required to meet the maximum heating and cooling demands of any of the zones in a temperature controlled space. Common references and comparators are employed for both heating and cooling controls.