Hazardous voltage protector for telephone line
US4106070A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 1, 1977 |
| Grant date | Aug 8, 1978 |
| Priority date | — |
| Expiry date | Feb 1, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02H3/32
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Telephone terminal equipments connected to the network through the device described herein are prevented from applying potentially human-hazardous voltages or currents to the network. The device includes a pair of bifilar relay coils, one in each connection to the central office. These operate an associated relay contact only when an unbalanced voltage or current condition occurs on the customer leads. A circuit path is thus completed to operate a second relay, which opens the connection between the customer terminal leads and the network leads; and establishes a path to ground through its own coils for the current from the unbalanced source. Means are included for assuring that the fraction of hazardous voltage appearing across the second relay remains essentially constant in the frequency range of 17 to 60 hertz. Only removal of the unbalanced current can release the relay and restore the network connection.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.