Soft-switching audiometer
US4448074A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 3, 1982 |
| Grant date | May 15, 1984 |
| Priority date | — |
| Expiry date | Feb 3, 2002 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K17/16
- WIPO fieldMedical technology
- WIPO sectorInstruments
Abstract
To provide both for soft-switching, that is, elimination of switching clicks, and rapid rise and decay of tone supply from a frequency generator (10) to an audio transducer (13), two electronic switches (11, 16) are provided, one interrupting connection from the source to an audio amplifier amplifying the signals for the transducer, and the other (16) effectively short-circuiting the amplifier, the switches having current transfer/time characteristics to provide for gradual current rise and current decay through the amplifier, and hence gradual rise and drop of the level of output from the transducer with sufficiently steep flanks, however, to effectively eliminate harmonics and hence high-frequency switching clicks. Typical switches use opto couplers with an instantaneous ON optical element such as a light emitting diode (30, 36) illuminating a photo resistor (31, 37) which has resistance change vs. time characteristics following an exponential function. Preferably, a third electronic switch, for example a field effect transistor (FET) is connected across the input of the amplifier. Timing circuits, which may provide for gradual current variation or delayed switching effects can b…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.