Abstract: A bilateral hearing instrument incorporates first and second units which could, for example, be worn by an individual having hearing deficiencies in both ears. One unit includes an audio input transducer coupled to a transceiver. The second unit includes a second audio input transducer coupled to a second transceiver which is coupled, wirelessly, to the first transceiver. An output of the second transceiver is coupled to an input port of a signal processor. A second input to the signal processor comes from the second audio input transducer. One output from the signal processor Is transmitted Tirelessly to the first unit for presentation to one ear of the user. The other output of the processor is coupled to an output transducer for the user's second ear. A single signal processor generates representations of audio output signals for both of the user's ears.

Abstract: A bias current compensator to supply the input bias current of a transistor. The bias current compensator may be used, for example, with the controlled amplifiers used in an automatic gain control system. The bias current compensator prevents bias current changes, caused by a varying control signal, from appearing in the output of the controlled amplifier. The bias current compensator includes a current source, first, second, and third transistors, and a feedback amplifier.

Abstract: A hearing aid that is compact and efficient and that provides a high degree of control over its frequency response and also over its output level versus input level characteristic. The frequency response control includes an adjustable four pole high pass filter and an adjustable four pole low pass filter, to define the pass band, and an adjustable slope filter, to define the slope within the pass band. The control over the output level versus input level characteristic includes an input AGC system with well defined, independent control of compression threshold and compression ratio, an adjustable peak clipper, and a selectable output AGC system that tracks the peak clipper setting.

Abstract: A hearing aid that is compact and efficient and that provides a high degree of control over its frequency response and also over its output level versus input level characteristic. The frequency response control includes an adjustable four pole high pass filter and an adjustable four pole low pass filter, to define the pass band, and an adjustable slope filter, to define the slope within the pass band. The control over the output level versus input level characteristic includes an input AGC system with well defined, independent control of compression threshold and compression ratio, an adjustable peak clipper, and a selectable output AGC system that tracks the peak clipper setting.

Abstract: A differential voltage threshold detector that may be used in a hearing aid circuit. The configuration includes an inherent differential/full wave operation, without the need for additional circuitry. The detector includes a differential transconductance stage, first and second "top" current mirrors (which respond to the transconductance stage), first and second "bottom" current mirrors (which respond to the top current mirrors) and a detector (which responds to the current levels in the mirrors). The detector effectively issues an output signal when the voltage applied to the threshold detector varies by more than a predetermined amount.

Abstract: A voltage regulator for producing first and second reference voltages. The regulator includes first and second transistors, of a first polarity, having coupled emitters, and third and fourth transistors, of a second polarity, having coupled emitters. A first amplifier is driven by the collectors of the second and third transistors, and provides a signal to the bases of the third and fourth transistors. A fifth transistor, of the first polarity, has its collector interconnected to the base of the second transistor, and the emitter of which is interconnected to the emitter of the first and second transistors. A second amplifier is driven by the collectors of the first and fourth transistors, and provides a signal to the bases of the first and fifth transistors. The wiper arm of a variable resistance whose end terminals are connected between the base and collector of the fifth transistor provides an adjustable reference voltage output over the range of the first and second reference voltages.

Abstract: A current source provides an output current that is substantially exponentially related to a difference between input voltages. The output current is also substantially linearly related to an input current. The current source includes first, second and third transistors interconnected to one another. The basic current source may be used as a "building block" to produce more complex control functions.

Abstract: An improved compansion system that more effectively increases the dynamic range of other circuit elements. The system includes both a compression circuit to limit the input signal amplitude for a circuit element, such as a filter, and an expansion circuit to receive and modify the output of the circuit element. The expansion circuit restores a substantially linear input-output amplitude relationship and may prevent substantial overloading in the circuit element, thereby increasing the dynamic range of the circuit element.

Abstract: A hearing aid that is compact and efficient and that provides a high degree of control over its frequency response and also over its output level versus input level characteristic. The frequency response control includes an adjustable four pole high pass filter and an adjustable four pole low pass filter, to define the pass band, and an adjustable slope filter, to define the slope within the pass band. The control over the output level versus input level characteristic includes an input AGC system with well defined, independent control of compression threshold and compression ratio, an adjustable peak clipper, and a selectable output AGC system that tracks the peak clipper setting.

Abstract: A system for suspending a receiver in a hearing aid and acoustically linking the receiver with the region external to the hearing aid. A shaped mandrel is placed inside the shell of the hearing aid and a liquid material is poured into the shell. The liquid material polymerizes to form an elastomer that is around the mandrel and in contact with the shell. The mandrel is then removed from the shell, leaving a receiver cavity and sound channel. A receiver is inserted into the receiver cavity. The receiver cavity holds the receiver, and the sound channel grippingly engages an acoustic output port on the receiver. The sound channel extends between the receiver and shell, acoustically linking the receiver with the external region.

Abstract: An electronic power control circuit for a hearing aid amplifier. The circuit includes a feedback stage, output stage, and output transducer. The feedback and output stages cooperatively define a current regulator that controls the current of the output stage. A variable resistor is provided for adjusting the maximum signal level that can be applied to the output transducer in the hearing aid. Such adjustment prohibits the output transducer from producing an undesirably loud acoustic output. Adjustment of the variable resistor also simultaneously varies both the quiescent current of the output stage and the hearing aid gain.

Abstract: An improved battery door structure is provided which has advantageous use in compact electronic apparatus, as for example a hearing aid, electronic watch, miniature calculator and other types of small battery operated devices. The structure includes a body member including a power source, such as a small battery. The structure is provided with a battery receptacle which has a hinged door, which may be opened and closed at will from the outside of the body member. In one preferred embodiment, the body member may be readily removable and replaceable from the remainder of the structure. The body member as a unit is provided with plastic members forming plastic hinge means for the battery door. The battery door includes hinge pivot pin means wherein the door and hinge pivot means preferably are molded as one piece.