Abstract: Test apparatus is disclosed for testing a gas-fired forced air heating system having a plurality of control elements. A monitoring device includes an indicator light adjacent to the thermostat for indicating a malfunction in the heating system, the monitoring device including condition-responsive switches for energizing the indicator in response to the absence of a stream of heated air when called for by the thermostat or in response to a malfunction in the thermostat. An analyzer comprises a plurality of indicator lights connectable through a selector switch to the power source and the heating system, the switch having an "OFF" condition for disconnecting the indicator lights, a "TEST" condition for checking the condition of the indicator lights and an "ON" condition for connecting the indicator lights respectively in parallel with corresponding heating system control elements to test the conditions thereof. Two embodiments of the analyzer are disclosed for use with different types of heating systems.

Abstract: A plurality of first logic processors are interconnected in a "ring" type network and individually exercise control over similar equipment group subsystems which individually contribute to the operation of an overall system. Each of the interconnected processors, in addition to its primary control function, monitors the safety of operation of the equipment group with which associated and the safety of operation of a "neighboring" equipment group. Redundant safety checks are thus performed on each equipment group and any discrepancies in the results of such safety checks are enunciated. A pair of further logic processors, in addition to performing other control functions including scheduling the operation of the individual equipment groups, redundantly check the safety of operation of the overall system.

Abstract: A burner control system has a field device and control logic for providing a control signal to change the state of the field device. A comparator that compares signals from field and the control logic comprises translation circuitry that is arranged to produce an output pulse train signal in response to a corresponding input pulse train signal, and power supply circuitry that has two logic inputs. The power supply circuitry supplies power to the translation circuitry only in response to a proper comparison between a field signal applied to one logic input and the control signal applied to the other logic input.

Abstract: A burner control system in which signals indicating the condition at various locations within the system are applied to a control circuit in the form of pulse trains, causing a continuous alternation of state of solid state switching elements therein. The system actuates a switch to open a fuel valve only when the level of the control circuit output signal is alternating, indicating that the said switching elements are operative. A comparison circuit compares the control circuit output signal with a signal denoting the condition of the fuel valve, to ensure proper operation of the fuel valve switch.