Abstract: Described are devices for automatically adapting electrical polarity from a power source to a specified output polarity for use by an electrical load. In one implementation, power adaptation circuitry comprising one or more bridge circuits accept electrical power of unspecified polarity and output specified polarity. The bridge circuit may comprise a plurality of field-effect transistors (FETs) configured such that a particular subset of the FETs are energized to conduct electric current to the outputs when a particular polarity is applied at inputs.

Abstract: A microphone assembly includes a microphone composed of a case having an open end and a printed circuit board. The printed circuit board is disposed in the open case end. The microphone assembly further includes a metal screen coupled to the case over the printed circuit board for shielding the microphone from electromagnetic interference. The metal screen includes several apertures.

Abstract: An acoustic signal level limiter provides a telephone handset/headset user with protection against loud audible signals generated within a communications system. The acoustic signal limiter comprises an acoustic signal level attenuation circuit and at least one acoustic signal level relay circuit. Once activated, the acoustic signal level attenuation circuit creates an attenuation network that attenuates an electrical acoustic signal transmitted through the communications system. Additional acoustic signal level relay circuits are activated to further attenuate the electrical acoustical signal to prevent the acoustic signal level attenuation circuit from operating in a deep saturation mode and provide further hearing safety for the telephone headset/handset user. A fuse in series and “Zener Zap” shunting transistor diodes may provide additional failsafe protection.

Abstract: An acoustic signal level limiter provides a telephone handset/headset user protection against loud audible signals generated within a communications system. The acoustic signal limiter comprises an acoustic signal level attenuation circuit and at least one acoustic signal level relay circuit. Once activated, the acoustic signal level attenuation circuit creates an attenuation network that attenuates an electrical acoustic signal transmitted through the communications system. Acoustic signal level relay circuits are activated to further attenuate the electrical acoustical signal to prevent the acoustic signal level attenuation circuit from operating in a deep saturation mode and provide further hearing safety for the telephone headset/handset user. A fuse in series and “Zener Zap” shunting transistor diodes provide assured higher signal level protection.

Abstract: Systems for a multifunction preamplifier microphone are disclosed. The system generally includes a microphone transducer and a configurable preamplifier circuit. The configurable preamplifier circuit includes an output terminal for outputting a signal, a configuration terminal for coupling one or more circuit components to the preamplifier circuit; and a housing containing the microphone transducer and configurable preamplifier circuit. Adjustable features include gain, frequency response and voice expansion timing characteristics.