Telephone privacy protector
US4747128A · kind A · utility
9Cited by
8References
11Claims
0Family size
Inventors
Key dates
| Filing date | May 22, 1986 |
| Grant date | May 24, 1988 |
| Priority date | — |
| Expiry date | May 22, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M9/02
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
This invention is a telephone privacy protector to be interposed between a common exchange line and each one of at least two telephones sharing the line. The device includes a voice connecting circuit connected between a respective phone and the line; a control circuit operatively engaging the connecting circuit, and having an on- and an off-state, and a trigger having a threshold voltage responsive to the line voltage controllingly engaging the control circuit to trigger it into its on-state to provide a voice connection between the telephone and the common line in response to the line voltage exceeding said threshold voltage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.