Abstract: A differential pressure control apparatus includes a switch responsive to a pneumatic differential pressure for signaling the actuation of a blower motor. A signal generating section is provided and controls the speed of a blower for regulating the differential pressure. This section includes first means for sensing a projected light beam and second means for modulating the light beam. The first means and the second means are positionably displaceable one to the other in response to the magnitude of the differential pressure. Two preferred embodiments are disclosed.

Abstract: A method of controlling a space heating system having a plurality of electrical resistance heaters includes the steps of computing the aggregate number of resistance heaters required to be energized to raise the actual temperature within a space to a set point temperature. This aggregate number may have integer and fractional components. One of the resistance heaters, denominated a controlled heater, is adapted both for continuous energization or for modulated control by intermittent energization. A group of second resistance heaters is adapted for continuous, staged energization, this group including a number of heaters equal to the integer component. Energization of the heaters comprising this group is preferably sequential after the lapse of a preselected interstage time delay between energization of the controlled heater and the first heater of the group.

Abstract: An apparatus useful in determining the value of a capacitor includes a first bilateral switch for flowing a charging current through a resistive element to an initially-depleted first capacitor of known value. The first capacitor is thereby charged to the potential of a trigger reference over a resulting first time period. A second bilateral switch is provided for flowing a charging current through the same resistive element to an initially-depleted second capacitor, thereby charging it to the potential of the same trigger reference over a resulting second time period. A device such as an oscilloscope or frequency counter is used for determining these time periods and the value of the unknown second capacitor may thereupon be computed using disclosed formulas.

Abstract: A capacitive pressure transducer of the deflecting diaphragm type is adapted to be coupled to a capacitance transducing circuit and includes a generally planar, electrically conductive base member support upon a first insulative substrate. A sensor member is supported upon a second insulative substrate in a generally parallel, spaced relationship from the base member and coacts with the base member to form a sensor capacitor. A reference member is generally coplanar with and in electrical isolation from the sensor member and coacts with the base member to form a reference capacitor. The sensor and reference members each have a plurality of segments interposed one with another. The sensor and reference capacitors have pressure-dependent capacitance values Cs and Cr respectively such that, for discrete pressures selected within an operative range of pressures, the output signals from the transducing circuit will be substantially linear.

Abstract: In general, a sealing apparatus for substantially preventing the flow of air through a damper assembly having a plurality of movable vanes includes a first, rigid sealing member having a generally circular cross-section and adapted to be attached to a first edge of a first movable vane. The first edge is movable through a first arc between a damper-open position and a damper-closed position. A second resilient sealing member has a generally rectangular cross-section and is adapted to be attached to a second edge of a second movable vane. The second edge is movable through a second arc between the damper-open and damper-closed positions. The sealing members make substantially line contact one with the other as the edges are moved toward the damper-closed position and are in substantially gas flow-preventing area contact one with the other when the vanes are in the damper-closed position.

Abstract: A stationary horizontal cylindrical reactor for the production of lead oxide utilizes a series of horizontal rotating blades to promote and maintain the oxidation reaction, to provide a particle size reduction and to effect centrifugal classification of the lead oxide produced in the reaction. The preheated reactor chamber is supplied with raw lead, air and water, and the use of the entire reactor chamber-blade interface as a reaction zone results in a highly energy efficient and high rate production process. The process is extremely versatile and can be used to produce low free lead (less than 1%) litharge (PbO) and high free lead or leady litharge on a consistent high volume basis.

Abstract: In general, an electronic control module includes a module frame adapted for swingable mounting to a rail member. The module includes a plurality of bus conductors constructed and arranged to engage the bus conductors of adjacent modules when mounted. The module also includes a plurality of electrically-conductive pads for engaging a circuit board which is attachable to the module frame. Terminals are included for the connective termination of external wiring. The module is swingably removable from a rail member while yet avoiding movement of a module which may be mounted adjacent thereto. The invention is particularly useful for the construction of electronic digital communication systems used with heating, ventilating and air conditioning equipment.

Abstract: The invention facilitates the reception of bus-transmitted digital signals in the presence of electrical noise and includes a transmitter adapted to be coupled to a two wire communication bus. The transmitter has a controllable transistor for switching one wire of the bus between zero and reference voltages, thereby generating digital output signals. A receiver is coupled to the bus for receiving digital input signals which define a first wave form and are transitory between a first voltage and a second voltage. The receiver includes an R-C circuit for shaping the first wave form to a second wave form and a hysteresis switch for providing a first output condition when the second wave form transcends through a first intermediate voltage in a first transition direction. A second output condition is provided when the second wave form transcends through a second intermediate voltage in a second transition direction.

Abstract: A method of preparing mixtures of dilute acid of varying final specific gravities utilizes microprocessor controlled mixing in two in-line stages. Process recycled or production reject acid or water is initially mixed with concentrated acid and directed to an intermediate heat exchanger for removing the exothermic heat generated during mixing. The specific gravity of the mixture exiting from the heat exchanger is continuously measured and fed to a microprocessor which calculates the deviation between the measured specific gravity and a preselected set point specific gravity which is greater than the desired final specific gravity. The calculated deviation is used to generate a control signal which, in turn, is applied to adjust the flow of concentrated acid until the measured specific gravity corresponds to the set point specific gravity.

Abstract: Membrane keyboard apparatus is disclosed including an insulator having a conductive sheet thereon providing a plurality of first electrode members in the form of an array of apertures, and a plurality of second electrode members located concentrically within and spaced from the periphery of the apertures of the first electrodes to form an array of individual switching units. The height of the conductive sheet is greater than the height of the second electrode members whereby the level of the top surfaces of the plurality of first electrode members is vertically spaced above the level of the top surfaces of the second electrode members. A flexible, conductive member is disposed in a spaced relation above and adjacent to the level of the top surfaces of the pluralities of first and second electrode members. An identification member having an array of indicia corresponding to the array of individual switching units is disposed in a spaced relation above and adjacent to the flexible conductor.

Abstract: A method of producing light emitting diodes of high quantum efficiency in mass production by utilizing an epitaxial deposition from a small size melt such that the substrate itself serves as a saturation source. A silicon doped gallium arsenide wafer is cleaned and etched by normal means and subsequently the wafer is precoated with a properly doped gallium master melt. The coated wafers are inserted into an epitaxial furnace and the gallium master melt effects solution of a portion of the gallium arsenide monocrystal substrate and finally the entire wafer is cooled, maintaining a temperature gradient causing epitaxial growth on the substrate.