Abstract: An electromagnetic tone generator having a pole piece adapted to be mounted on a circuit board and to be incorporated in the circuitry thereof, an electromagnetic coil sub-assembly adapted for mounting on a coil carrying portion of the pole piece and to be separately fastened electrically and physically to the circuit board, and a sound transducer sub-assembly including a housing defining a sound cavity and a diaphragm closing the latter and held by a retainer ring detachably fastened to the housing, the sound transducer sub-assembly adapted to be tested for sound prior to assembly and for mounting on and detachable connection with the pole piece, the retainer ring being detachably fastened to the housing so that in the disassembled condition of the sound transducer sub-assembly the ring is readily removable for replacement or servicing of critical parts of the sub-assembly, and in the assembled condition of the sound transducer sub-assembly the latter is held by the pole piece spaced from the circuit board t

Abstract: A tone generator for producing an audible sound for a predetermined time period in response to the occurrence of one or more predetermined conditions. The tone generator comprises a diaphragm mounted within a resonant sound cavity that is activated by an electromagnetic assembly which is in turn driven by the output signal from an oscillator circuit. The control logic and timing circuit for the tone generator includes a unique PTC subassembly that provides a timed logic signal for controlling the activations of the diaphragm, as well as an independently generated signal for contemporaneously activating a lamp which provides a visual indication of the detected predetermined condition. The control logic and timing circuit is adapted to produce the proper timed logic signal despite the absence of a lamp in the circuit or a lamp failure.

Abstract: A tone generator for producing an audible sound for a predetermined time period in response to the occurrence of one or more predetermined conditions. The tone generator comprises a diaphragm mounted within a resonant sound cavity that is activated by an electromagnetic assembly which is in turn driven by the output signal from an oscillator circuit. The control logic and timing circuit for the tone generator includes a unique PTC subassembly that provides a timed logic signal for controlling the activations of the diaphragm, as well as an independently generated signal for contemporaneously activating a lamp which provides a visual indication of the detected predetermined condition. The control logic and timing circuit is adapted to produce the proper timed logic signal despite the absence of a lamp in the circuit or a lamp failure.

Abstract: A control circuit for a tone generator that is adapted to cause the tone generator to produce a plurality of readily distinguishable audible sounds, including a chime sound, a pulse tone and a steady tone. The control circuit has particular application for use on an automobile to monitor such conditions as "seat belts buckled", "headlamps on", and "key in the ignition". The control circuit includes three oscillator circuits that are adapted to produce square wave output signals at three different frequencies. The chime sound is generated by pulse width modulating the highest frequency signal and "restriking" the decaying sound at the frequency of the lowest frequency oscillator. The steady tone is produced by driving the tone generator directly with the output signal from the highest frequency oscillator. To generate the pulse tone, the highest frequency oscillator is repeatedly enabled and disabled in accordance with the output signal from the middle frequency oscillator.

Abstract: A driver circuit for a tone generator that is adapted to cause the tone generator to produce a pleasant sounding chime. The circuit comprises high and low frequency oscillator circuits whose decaying sawtooth type outputs are summed and modulated to produce the desired chime effect.

Abstract: A thermomechanical vacuum regulator adapted for use in automatic temperature control systems includes a bimetal strip which flexes in accordance with the temperature of air stream whose temperature is to be controlled. The bimetal strip positions a whiffle tree beam which carries a vacuum valve for communicating a source of vacuum with a chamber within which vacuum is regulated, and a vent valve for communicating the chamber with a source of ambient air. The vent valve seat is located on a floating diaphragm which forms one wall of the chamber. In alternative embodiments, one of the valves is replaced by an orifice and column.

Abstract: A pressure responsive diaphragm is attached to a substrate carrying a thick film metallic coating covered by a dielectric glass coating so that the diaphragm and thick film coating comprise a pressure variable capacitor. Changes in pressure difference across the diaphragm force the diaphragm to roll against the glass to vary the area of diaphragm in contact with the glass, thus changing the capacity.