Abstract: A temperature control system for a building is disclosed utilizing a central demand limit controller. The system includes a number of control modules or thermostats that have both proportional error and integral error functions. The integral error is reset at intervals by an interstage differential to drop single stages of air conditioning. This reduces demand until the maximum allowed demand is met. The integral error function is a timed function and the stages return in a random manner to restore setpoint temperature.

Abstract: An asynchronous one way digital data communication system is disclosed in which a first microcomputer produces a series of groups of pulses at a first port representative of digits in an information packet to be transmitted, the groups being separated by strobe pulses at a second port. The pulses drive switches in two current paths to control current therethrough supplied by a receiver module including a second microcomputer having a serial input port connected to an internal counter and an interrupt port. Current detectors supply pulses corresponding to currents in the paths to the serial input and interrupt ports, from which the second microcomputer reproduces the information packet.

Abstract: A microcomputer utilizing a crystal controlled clock and a power line responsive clock operates both the control system and into a safety timing means. The safety timing means can take the form of a pair of retriggerable monostable multivibrators that are operated to monitor the microcomputer along with a feedback circuit from a load control means. The feedback from the load control means senses the status of a safety switch means and provides the microcomputer with the ability to monitor and be monitored for safe operation.

Abstract: An air conditioning system furnishing temperature conditioned air to a plurality of zones each of which has its own zone damper controlled by its own space thermostat. The system has an air discharge temperature sensor downstream of the temperature conditioning heat exchanger which is connected to a microprocessor controller for controlling a plurality of stages of temperature conditioning apparatus such as heating or cooling apparatus and a damper motor control for controlling the entry of outdoor air into the system.

Abstract: A control logic means or microcomputer controlled burner control system has been disclosed. The system utilizes a safety relay that has contacts that are in series with all of the other loads for the system. The safety relay contacts are checked prior to operation of the system to verify their ability to open the load circuit. The operation of the electronics for the control of the safety relay are regularly checked during the operation of the system by a combination of feedback circuits from the electronics, and from the final control element for the various loads.