Amplifiers – Signal feedback – Combined with control of bias voltage of signal amplifier
Patent
1976-11-08
1977-09-20
Olms, Douglas W.
Amplifiers
Signal feedback
Combined with control of bias voltage of signal amplifier
179107R, 330 2, G01R 2500
Patent
active
040499308
ABSTRACT:
Disclosed is a malfunction detection system for detecting malfunctions in electrical signal processing circuits. In a particular embodiment shown, malfunctions of a hearing aid in the form of frequency distortion and/or inadequate amplification by the hearing aid amplifier, as well as weakening of the hearing aid power supply are detectable. A test signal is generated and a timed switching circuit periodically applies the test signal to the input of the hearing aid amplifier in place of the input signal from the microphone. The resulting amplifier output is compared with the input test signal used as a reference signal. The hearing aid battery voltage is also periodically compared to a reference voltage. Deviations from the references beyond preset limits cause a warning system to operate. In the method of the invention, the input to a circuit to be tested is periodically interrupted and, for a fixed test time interval, a test signal is applied to the circuit to be tested. The output of the circuit to be tested is compared with a reference signal, and deviation in amplitude and/or frequency between the two signals beyond preset limits triggers a warning. During the test time interval, the voltage level of the power supply for the circuit to be tested is also compared to a reference voltage, and the warning system is triggered if the power supply voltage falls below the reference voltage.
REFERENCES:
patent: 2425002 (1947-08-01), Pfleger
patent: 3833856 (1974-09-01), Roeschlein
patent: 3879662 (1975-04-01), Barneck
patent: 3879717 (1975-04-01), Gruensfelder
patent: 3979657 (1976-09-01), Yorksie
"Maintenance" in ATE Journal, vol. 17, No. 2, Apr. 1961, by King et al., pp. 84-91.
Fletcher James C. Administrator of the National Aeronautics and Space
Kessinger Roger L.
Manning John R.
Marnock Marvin J.
Matthews Marvin F.
Olms Douglas W.
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