Intercom system for a key telephone system
US4037058A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 6, 1976 |
| Grant date | Jul 19, 1977 |
| Priority date | — |
| Expiry date | May 6, 1996 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M9/002
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A control circuit including a mechanical interrupter provides a plurality of interrupted ringing signal bursts when one of a plurality of intercom stations goes off-hook and first initiates a call to another of the plurality of intercom stations. The interrupter also provides an interrupted voltage to cause a button lamp at the another of the plurality of intercom stations to flash. A call selector circuit and a call routing circuit are coupled to the control circuit and the plurality of intercom stations to provide a connection between the one and the another of the plurality of intercom stations to enable the interrupted ringing signal bursts to be conducted on the connection to the another of the plurality of intercom stations. Logic circuitry is coupled to the plurality of intercom stations and the control circuit to detect when the one and the another of the plurality of intercom stations are both off-hook. When this condition is detected the interrupted ringing signal bursts are stopped and the button lamp is caused to glow steadily.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.