Intercom telephone
US4996709A · kind A · utility
90Cited by
49References
27Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | May 12, 1988 |
| Grant date | Feb 26, 1991 |
| Priority date | — |
| Expiry date | May 12, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M9/027
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An intercom system for use in combination with a multi-line telephone system wherein the intercom system utilizes the same wire pair for communications between intercom units that is used for normal telephone communications. The intercom system transmits voice signals on two or more frequency modulated channels over a wire pair of a local telephone network. Each intercom unit includes a microprocessor which controls communication activity and protocol in each unit and communicates with other intercom unit miroprocessors via a separate frequency modulated digital signal channel.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.