Digital telephone set having an emergency switching function and communication system having the same
US5142571A · kind A · utility
35Cited by
2References
16Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | May 21, 1991 |
| Grant date | Aug 25, 1992 |
| Priority date | — |
| Expiry date | May 21, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/253
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A digital telephone set includes a digital telephone circuit and an emergency analog circuit. Normally, the digital telephone circuit is made active so that a handset provided in common therewith is connected to a digital transmission line. In an emergency, the emergency analog circuit is made active instead of the digital telephone circuit so that the handset is connected to an analog transmission line. A dial key pad unit and a speaker are provided in common with the digital telephone circuit and the emergency analog circuit.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.