Dual mode telephone subscriber loop current detector
US4087646A · kind A · utility
17Cited by
3References
4Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Jan 28, 1977 |
| Grant date | May 2, 1978 |
| Priority date | — |
| Expiry date | Jan 28, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M19/026
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A detector circuit is shown for detecting off-hook and dial pulse signals in a telephone system which, under the control of a ringing relay, reconfigures itself to provide ring-trip detection. The detection circuit includes a bridge which is responsive to circulating loop currents, while at the same time unresponsive to longitudinally balanced currents, and a two-stage voltage level detector circuit. An RC timing circuit is included between the two stages to insure that the detector is unresponsive to short duration pulses and, at the same time, once energized, will bridge over short duration interruptions of detected pulses.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.