Hazardous voltage protection circuit
US4264787A · kind A · utility
2Cited by
8References
10Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Dec 31, 1979 |
| Grant date | Apr 28, 1981 |
| Priority date | — |
| Expiry date | Dec 31, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/745
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A circuit for protecting telephone lines from AC hazardous voltages. The circuit includes an amplitude discriminator triggered at a predetermined voltage level connected to the telephone lines, and providing an output pulse for each zero voltage crossover of the hazardous voltage. A digital pulse counter counts a predetermined number of output pulses from the amplitude discriminator, which in turn operates a switch after the predetermined number of pulses are counted, opening the telephone lines between the central office and the telephone instrument until the hazardous voltage has been removed from the lines.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.