Abstract: A hearing aid having a microphone (10), a microcomputer (12) for digital signal processing of digitized microphone signals and an electroacoustic converter (14) for acoustic reproduction of the processed digitized signals, is equipped with at least one further sensor (16, 18) responsive to signals outside the acoustical range of audibility. These further sensor signals are processed according to a different program stored in a second memory (19) and supplied as additional data via an output (B2) of the microcomputer (12) preferably to the electro-acoustical converter (14). As a result, data such as the signals of a traffic light transmitter, signals from a paging system, or signals announcing a telephone call, door bell or the like, can be superimposed on the normal auditory functions. By appropriately coordinate signal trains, for example generated in accordance with the program stored in the second memory, a hearing-impaired person can easily distinguish among these additional functions.

Abstract: An audiometer which can be battery operated, is reliable and economical in current consumption has a digital control unit (10) which controls a LCD in matric form (11, 26). The digital control unit, in its simplest form, includes a data input stage (12) having two inputs (16, 18) receiving, respectively, input signals representative of amplitude and tone, or a spoken word, and a further input (14) which is test-person controlled, to provide a perception signal, operated by the person to be tested when the level of a certain tone, generated by a tone generator (G, 21) is perceived, or a spoken word is correctly heard. The data input stage is connected to a data bus which provides the respective data to a driver circuit (24) to drive the LCD matrix.

Abstract: To provide for tuning of an oscillator circuit, a plurality of resistors are selectively connectable in the circuit. To provide for reproducible, accurate oscillation frequency in accordance with switching of a respective resistor in dependence on a digital input signal, electronic switches are respectively connected to the resistors to connect them in circuit in the oscillator to thereby eliminate variable contact resistances of mechanical switches. A digital frequency control signal is generated by placing a movable mask or pattern with openings therein between an array, for example a linear strip of light emitting diodes, and a similar strip of photo transistors, the respective energization of which is determined by openings in the diaphragm. The signals from the photo transistors are stored in a memory, typically a group of flip-flops, for application to the electronic switches controlling connection of the respective resistors in the oscillator circuit.