Two-wire television interphone system
US5032820A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 14, 1989 |
| Grant date | Jul 16, 1991 |
| Priority date | — |
| Expiry date | Nov 14, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M11/025
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Two-wire television interphone system is arranged to discriminate by a line voltage discriminator incorporated in a master device a line voltage variation due to a calling operation on the side of a branch device, to actuate a voltage controller in the branch device to shift the system from standby state to operation state, and to drive a call signal generator in the branch device for actuation of a call signal receiver in the master device. The system is thus made to have a power supply circuit energized for a power supply to the system only when required for effecting the calling operation, talking between the both devices, and so on.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.