Patent · US Expired

Key telephone system optically coupled protective coupler

US4132870A · kind A · utility

4Cited by
1References
9Claims
0Family size

Assignee

Inventor

Key dates

Filing dateNov 3, 1977
Grant dateJan 2, 1979
Priority date—
Expiry dateNov 3, 1997

Classification

  • Technology area (CPC H)Electricity
  • CPC primaryH04M9/006
  • WIPO fieldTelecommunications
  • WIPO sectorElectrical engineering

Abstract

There is disclosed a protective coupler circuit of the circuit breaker type having a relay contact inserted in the communication line between the key telephone station and the central office in order to protect the central office line from hazardous voltages. A longitudinal unbalance detector is coupled with a metallic high voltage detector to control the relay operation. Circuitry is provided to operate in conjunction with the ring detection circuitry of the key telephone unit to insure proper circuit operation when ringing potential is present on the communication line even though that potential is over the threshold level of the hazardous voltage protector.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.