Device for adding intercom functions to a phone system
US4769837A · kind A · utility
91Cited by
8References
3Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | May 4, 1987 |
| Grant date | Sep 6, 1988 |
| Priority date | — |
| Expiry date | May 4, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M9/02
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A device for adding intercom functions to a residential or small business phone system uses existing telephone equipment and wiring. The device attaches to the incoming telephone line to switch telephone calls and generate user coded ringing signals. The invention allows the user to simultaneously use existing telephone equipment as an intercom system and for normal outside telephone use.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.