Intrinsically safe telephone
US5136630A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 13, 1990 |
| Grant date | Aug 4, 1992 |
| Priority date | — |
| Expiry date | Jul 13, 2010 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02D30/70
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An intrinsically safe telephone as provided for use in hazardous areas. The telephone includes a single line instrument located in the hazardous area which, in turn, is coupled by a two-wire transmission path to a shunt diode barrier and a telephone line interface located in a safe environment. The telephone line interface reduces power of incoming ringing and audio signals. The telephone line interface further includes an off-hook indicating circuit which senses when the single line instrument is off-hook. The intrinsically safe telephone is useful in all hazardous environments as classified by the National Electrical Code and requires no explosion-proof housing.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.