Means for improving the dynamic range of an analog/digital converter in a digital telephone answering machine
US5289529A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 4, 1990 |
| Grant date | Feb 22, 1994 |
| Priority date | — |
| Expiry date | Oct 4, 2010 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/6008
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An automatic gain controller uses a voltage controlled amplifier coupled to an averaging circuit that feeds back into the amplifier. The averaging circuit supplies a controlling voltage that keeps the amplifier output voltage tending towards a certain reference level. When the amplifier output is generally high, the averaging circuit output is also generally high and the reverse is also true for low signals. For low averaging circuit output voltages corresponding to low intensity signals, amplification of the signal by the amplifier is enhanced or augmented. The result is to boost the signal of low intensity signals significantly, compressing the dynamic range of an incoming signal received from a phone. This reduces the variance of an incoming phone line signal for an analog to digital converter (ADC) in a digital telephone answering device, and the effective dynamic range of the ADC is closer to optimum. A scaling circuit couples the signal from the automatic gain controller to the ADC.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.