Personal branch exchange system
US4633040A · kind A · utility
1Cited by
5References
13Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Oct 25, 1984 |
| Grant date | Dec 30, 1986 |
| Priority date | — |
| Expiry date | Oct 25, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/82
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A personal branch exchange telephone system including improved interface circuitry to couple the system to outside telephone lines as well as to individual telephone sets on extension lines in the PBX system. The PBX system is connected to the telephone lines only through electromagnetic coupling and circuitry is provided to detect both ringing signals and loop current carried by the telephone lines.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.