Multiple line self-contained telephone
US4677662A · kind A · utility
5Cited by
3References
5Claims
0Family size
Inventor
Key dates
| Filing date | Aug 23, 1984 |
| Grant date | Jun 30, 1987 |
| Priority date | — |
| Expiry date | Aug 23, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/82
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A detection circuit is provided for indicating whether a telephone line is in use or is available or is on hold. The simplified circuit can be incorporated within a telephone instrument so that no external circuitry is required.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.