Abstract: Communication between the various elements of HVAC systems is effected by means of low-cost, low-power, narrow-band AM SAW-stabilized transmitters 21, 27, 39, 86 and receivers 18, 28, 47, 89. A residential embodiment (FIG. 1) transmits temperature information from each room of the house to a master control 24, which is used to control the HVAC demand and to control the damper in the corresponding room. In a first commercial building embodiment (FIGS. 2 and 3), thermostat/transceiver 61-66 assemblies transmit not only demand and control information from the corresponding thermostat 78 (with switches), but relay information transmitted from other thermostat/transceiver assemblies, whereby messages are retransmitted from one floor to the next to overcome the high attenuation of commercial building construction in reaching rooftop HVAC systems 71-76. In a second commercial building embodiment (FIG.

Abstract: A silicon capacitive microsensor which is sensitive to acceleration forces includes a silicon capacitive sensing element 10 comprising three silicon layers 12,16,26 having glass dielectric layers 14,24 between each pair of silicon layers with the middle silicon layer 16 consisting of a proof mass 18 suspended between the two glass dielectric layers 14,24 by a silicon hinge 20 which is connected to a slightly thicker silicon support layer 17 around the periphery (FIG. 3 ) between the glass layers 14,24 (FIG. 1 ). Three metallic bond pads 40,42,44 on the surface 45 of the silicon layers 26,16,12, respectively, are soldered to circuit trace pads 108 on a circuit board 100 which has a glass upper layer 104 and a silicon support layer 102. The thermal expansion coefficient between the glass layer 104 and the sensing element 10 are substantially the same, thereby minimizing thermally induced stresses on the sensing element 10 and minimizing inaccuracies associated therewith.

Abstract: An obstruction detection system includes emitters, a sensor, and obstruction detection circuitry. The emitters mounted along the top of an opening radiate a plane of light toward the floor. The plane of light intersects the floor and creates a floorline at the intersection of the plane of light and the floor. The plane of light also intersects the door edge and creates a door edge line at the intersection of the door edge and the plane of light. A sensor, located outside the plane of light, monitors the opening so that the presence of the obstruction can be detected from a change in a received light pattern of the floorline, the door edge line, and from reflections from an obstruction in the plane of light. The sensor provides an output signal in response to the received light pattern to a means for analyzing said sensor output signal for obstruction detection.

Abstract: A fiber optic rotation sensor includes a fiber optic coil with light beams counterpropagating therein where the beams are phase modulated with a squarewave carrier at the coil eigenfrequency. The beams recombine at the coil output with a resultant optical intensity which is a measure of the change in sensor rotation rate. The recombined signal also contains an error component due to squarewave carrier imperfections which cause high frequency spikes in the modulated rate signal resulting in rotational rate bias errors. The rotational rate bias errors are reduced by demodulating the modulated rate signal with a demodulator reference signal uniformly phase dithered about the carrier signal.

Abstract: A fiber optic rotation sensor having a pair of light beams counterpropagating in a loop includes a phase modulator for modulating the waves at a first frequency, upon exiting the loop the waves are combined into a light intensity signal indicative of rotation rate and is sensed. A signal at the first frequency is quadrature phase shifted by a lower frequency signal and summed with the sensed rate signal, an amplifier amplifies the summed signals, the amplifier also inherently induces undesirable phase shifts by an equal amount in both the sensed rate signal and the quadrature signal. The quadrature signal is demodulated and used in feedback fashion to control the phase of a variable phase shifter which provides a signal at the first frequency whose phase is shifted by an amount equal to the undesirable phase shift of the sensed rate signal, the variable phase shifter signal and the sensed rate signal being provided to a demodulator to demodulate rotation rate information from the sensed rate signal.

Abstract: A temperature sensing semiconductor device is fabricated in the same substrate as a semiconductor light source. A sensing voltage generated across the sensing device is proportional to light source temperature. The sensing voltage is amplified by an operational amplifier, and converted into a digital signal by an analog to digital converter. A microprocessor converts the digital signal into a corresponding temperature signal using a look-up table.