Automatic linear compression circuit
US4634960A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 4, 1985 |
| Grant date | Jan 6, 1987 |
| Priority date | — |
| Expiry date | Oct 4, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03H17/00
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An automatic linear compression circuit for a telephone "handsfree" loudspeaker is provided. The circuit consists of a variable attenuator the level of attenuation of which is controlled by the input signal level. The input signal is passed through a positive peak detector to obtain a time averaged signal corresponding to the average positive peak values of the input signal and this time averaged signal is compared against a time increasing reference voltage. As long as the reference voltage is below the value of the time averaged signal a positive attenuator control signal is derived. This positive control signal keeps the attenuator portion of the circuit operative. In the attenuator the input voltage is sampled to a first capacitor. The first capacitor is subsequently connected to and disconnected from a second capacitor a number of times as long as the positive attenuator control signal is present. Each time this is done the voltage on the first capacitor is reduced by a factor depending on the capacitances of the two capacitors. After a predetermined time the voltage remaining on the first capacitor is passed through buffers and another capacitor to provide an attenuated outpu…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.