Abstract: An apparatus for controlling an electrical appliance coupled with an output terminus and configured to operate in response to an alternating input signal, such as input AC power. The apparatus comprises a reference signal generator for receiving the input signal and generating a reference signal (either V.sub.RAMP or V.sub.CONTROL) in response to the input signal, and a control circuit for controlling connection of the input signal to the output terminus in response to the reference signal and to a user-defined set-point signal. The control circuit is coupled with the reference signal generator and with a set-point terminal. The set-point terminal receives the set-point signal and the control circuit controls connection of the input signal with the output terminus in response to a predetermined relationship between the reference signal and the set-point signal; the apparatus is capable of generating a modified periodically interrupted AC power output based on an AC power input.

Abstract: A proportional plus integral controller operates an actuator in an HVAC system. The controller includes a setpoint circuit for providing a setpoint signal representative of a desired room temperature, a sensor circuit for providing a sensor signal representative of the actual room temperature, an error generator for generating an error signal proportional to the difference between the setpoint signal and the sensor signal, and an integrator for generating a control signal related to the time integral of the error signal. The setpoint and sensor signals are derived from a common voltage reference, so that accuracy of the controller is substantially independent of fluctuations of that reference. The integrator includes a capacitance multiplier that provides highly accurate integration of the error signal and a switch for selecting either proportional plus integral or proportional only control.

Abstract: A control device for energizing and de-energizing temperature changing devices having a primary control unit and a secondary control unit is provided. The primary control unit includes means for sensing an external temperature and generating a signal (Ps) having a value proportional to the external temperature, means for generating a set point signal (Psp), representing one end of a predetermined primary temperature range, and means for generating a differential signal (Pd), representing the difference between signal Psp and the other end of the predetermined primary temperature range are included. Additionally, the primary unit includes a primary switch for connecting power to at least one temperature changing device which is opened and closed in response to combinations of signals Ps, Psp and Pd.