Microphone circuit
US4922547A · kind A · utility
13Cited by
9References
5Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Dec 14, 1987 |
| Grant date | May 1, 1990 |
| Priority date | — |
| Expiry date | Dec 14, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/605
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A microphone circuit for a mobile telephone is capable of operations in either of two modes, i.e. in a hands-free or a push-to-talk mode. A constant current circuit is coupled in parallel with the microphone to preclude a change in a DC bias voltage responsive to switch operations, especially in a push-to-talk mode. A voltage comparator compares the bias voltage with a reference to detect control signals and selects a preferred mode of operation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.