Abstract: An analog thermometer of the bimetal coil type has a rotatable hub carrying the bimetal coil. The thermometer is calibrated to indicate exact ambient temperature by rotating the hub to the proper angular position. The hub and the base supporting the hub are designed to allow fabrication as a unitary molded plastic article. A preferred embodiment of this design comprises at least four inwardly projecting tabs carried in an opening in the base and spaced from each other around the periphery of the hole. The hub has at least four outwardly projecting tabs spaced about its periphery. The angles which each of the hub's tabs and the hole's tabs subtend and the tabs' axial positions allow the hub to be rotated to interleave the tabs, restraining the hub in a predetermined axial position and frictionally fixing the hub in the angular position for calibration.

Abstract: An electrostatic air cleaner has at least one hole in one of the plates over which air with charged dirt particles is passed. A light source is mounted adjacent to the hole so as to direct its light through the hole. A light sensor detects the level of light passing through the hole. As dirt particles deposit on the plate, they fill in the hole over a period of time, reducing the amount of light passing through the hole. It is possible by measuring the amount of light passing through the hole, to determine the amount of dirt deposited on the plate. In a preferred embodiment, each of the plates contain a hole in alignment with each of the other plates' holes so that light from a single light source can pass through each of the holes. Such a configuration allows both the light source and the light sensor to be located outside of the entire group of plates.

Abstract: A space heating system with a controllable air humidification capability calculates a theoretical value for the temperature of the interior surface of the space's windows. The system controls humidity in the space to a level just below that at which water will condense on the window surfaces.

Abstract: A communication system comprises a remote switching module having two signal terminals connected by just two conductors to the signal terminals of a local decoding module. Power is directly provided only to the local decoding module, which applies DC voltage of a first level across the conductors. The remote switching module has a voltage regulator which provides power of a second voltage level lower than the first level for operating a control unit in the switching module. The control unit controls a variable impedance having higher and lower impedance levels and which is connected across the switching module's signal terminals. The decoding module can detect the different impedance levels by sensing the current flow on the conductors. The switching module communicates with the decoding module by modulating the time intervals between changes in impedance levels.

Abstract: A thermostat for controlling an air conditioning system has a selectable cycling rate. A manually variable resistor element is connected in parallel with the thermostat's standard anticipator resistor. In a preferred embodiment, the manually variable resistor element comprises a series circuit formed from a manually operable switch in series connection with a cycling modifier anticipator resistor is connected across the power terminals of the thermostat. By closing the switch, additional heat is supplied to the thermostat's temperature sensing element during the times when the thermostat is not providing power to the air conditioning system. The additional heat causes the thermostat to cycle the air conditioning unit more rapidly.

Abstract: A linear hydraulic actuator has a reciprocating pump which provides pressurized hydraulic fluid contained in a reservoir to a hydraulic cylinder in which slides a piston which supplies the actuator output. A diverter valve in flow communication with the pressurized hydraulic fluid has an adjustment shaft allowing manual adjustment of the rate of flow of pressurized hydraulic fluid to the cylinder. Preferably the pump is immersed in the hydraulic fluid held by the reservoir, and the adjustment shaft of the diverter valve penetrates a wall of the reservoir to allow external adjustment of the diverter valve.

Abstract: A thermostat has terminals to receive at least two temperature sensor signals, and changes the one of these terminals which provides the feedback signal for temperature control responsive to a detected condition. This condition may be a manual input, expiry of a time interval, reaching a time of day, or the relative magnitudes of the temperatures encoded in the sensor signals.

Abstract: A computer has access to a number of data items available from at least one data source. The computer receives requests for the values of certain of these data items from a number of different clients which may be either devices external to the computer or application programs operating in a multitasking environment within the computer. As each request is received from a client, it is stored in a data item table. The computer replies to each client request in the data item table with a data item value available somewhere in the data item table. The computer updates older data item values held by the data item table by requesting those data item values from the data sources which provide them. The data item values supplied to clients are those from previously received data source replies if these replies are not too old.

Abstract: A photoconductor has an active layer of gallium nitride having approximately 10.sup.15 to 5.times.10.sup.15 net donor sites per cubic centimeter and is sensitive to UV radiation. This photoconductor has at least one of a sheet resistance in the approximate range of 10.sup.4 to 5.times.10.sup.6 ohms/unit area and a relatively low level of photoluminescence in the range from about 430-450 nm when excited with light of energy higher than the bandgap energy of 3.4 eV. These criteria tend to define similar semiconductor materials which can form the active layer of an ultraviolet (UV) photodetector having the improved characteristics of a relatively low dark resistance, high sensitivity over at least a range of UV radiation intensity, and decreasing gain with increasing UV radiation.

Abstract: A housing for electrical equipment such as an electronic thermostat has a panel in which is a keypad having a number of keys for manual entry of data, and a cover which can be moved into position to cover the keypad. The cover includes a pushrod which passes through a hole in the cover which is aligned with one of the keys while the cover covers the keypad. The pushrod is supported by a support arm assembly mounted on the cover surface at preselected mounting points and having a brace arm arranged to reduce stress on the mounting points and reduce friction and binding during operation. The topology of the pushrod, support arm assembly, cover, and a stop integral with the cover and which limits travel of the pushrod, cooperate to allow the pushrod and support arm assembly to be an integral unit and yet to be assembled to form the complete cover.

Abstract: A control system and method for providing a nonlinear response for a single input-single output system. A system output is measured and compared against a predetermined set point. An error signal from this measurement is used to identify an entry in a lookup table. The entry is a control signal used to vary the input to the system so as to reach a desired output. The lookup table entries are configured so that as the output reaches the desired set point, smaller and smaller incremental steps are taken in varying the input.

Abstract: A mechanism for transferring torque from a motor to a gear train through a magnetic hysteresis slip clutch has a feature for disconnecting the motor from the gear train. A cup element of the clutch is carried on a shaft and can be shifted along the shaft's axis. The cup element has a magnetic member on its outer surface and an interior hysteresis layer. An electromagnet can magnetically apply force to the magnetic member to axially shift the cup element, and by so doing can shift a drive gear carried on the cup element into and out of mesh with a first gear of the gear train. In a preferred embodiment, the cup element shifts the drive gear into mesh with the gear train's first gear when the electromagnet is energized and magnetically applies force to the magnetic member, and allows magnetic force applied to the hysteresis layer by a permanent magnet element of the clutch to shift the drive gear into its unmeshed position when the electromagnet is deenergized and does not apply force to the magnetic member.

Abstract: An electrically operated actuator stores power in a capacitor for returning the actuator output element to a preselected position upon power failure. The actuator has a controller having input power terminals connected across the capacitor and control terminals for controlling the power applied from the input power terminals to the motor which comprises the actuator's prime mover. A sensor monitors the presence of power provided to the controller's input power terminals. When failure of this power is sensed, the capacitor current flows to the controller, and the sensor applies signals to an override circuit of the controller causing the controller to apply current from the capacitor to the actuator motor in a way which drives the actuator toward the preselected position. A properly selected capacitor is capable of supplying adequate current over a period of time sufficient to return the actuator to the preselected position.

Abstract: An electromechanical thermostat has a fixed value voltage anticipator resistor and a variable anticipator resistor for series connection with the load. This allows a single thermostat to control either a high efficiency furnace requiring a relatively low cycle rate or a furnace of conventional efficiency which can function at a higher cycle rate. Preferably, the voltage anticipator resistor is selected to give the cycle rate required by high efficiency furnaces when the resistance of the variable anticipator resistor is set to zero ohms. If the thermostat is shipped with the variable resistor set to zero ohms, the installer will not have to adjust the variable resistor whenever the thermostat is installed in a system requiring that cycle rate.

Abstract: A display system provides a real time display on its display screen of the present and recent past operating history of an operating system. The operating system provides a signal to the display system in real time which encodes the current operating state of the operating system. For each operating state, a line is displayed in the display screen at a coordinate position which associates the line with the operating state. Each of these lines is coordinated with a time scale running along the screen which indicates the actual time intervals during which the various states existed.

Abstract: An infrared imaging array of thermoelectric sensors has a plurality of electrically connected microbridge subsensors comprising each sensor of the array. Each subsensor consists of a short span microbridge lying across a relatively small pit. The use of many of such subsensors for each sensor rather than a single large area microbridge sensor for a single pixel allows each pixel to be made large enough to give good sensitivity in either vacuum or gas-filled designs, and at the same time avoid the reduced fabrication yield which results when sensors span large pits.