Telephone group listening systems
US4330690A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 5, 1980 |
| Grant date | May 18, 1982 |
| Priority date | — |
| Expiry date | May 5, 2000 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M9/08
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A telephone group listening system is one in which one member of an assembled group has a telephone for communication with a remote party while the other members may only listen to the communication through the agency of a loudspeaker. The system is subject to the Larsen effect on call answering or clear down if the telephone handset is normally sited close to the loudspeaker. This effect is overcome by including a proximity switch in the loudspeaker circuit, the switch being triggered by a change in the level of coupling of a capacitively or inductively coupled circuit, the coupling being dependent on the closeness of the speaker's body to the switch or on the separation of the handset and the loudspeaker.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.