Method and apparatus for an improved ring trip detection telephone circuit
US4677664A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 21, 1984 |
| Grant date | Jun 30, 1987 |
| Priority date | — |
| Expiry date | Nov 21, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M19/026
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A telephone circuit for ring trip detection that can be monolithically integrated, includes a current transducer coupled to a user's telephone line, and an integrator circuit. The output current of the current transducer is proportional to the line current until equal and opposite threshold values are reached. When the line current threshold values are exceeded, the transducer output current is constant. The transducer output current is integrated by the integrator circuit over at least one complete cycle. When a telephone headset is removed, a direct current is applied to the ringing signal current resulting in asymmetry in the half-cycles of the transducer output current. The asymmetry provides a non-zero integrated current for a complete cycle. When the integrated value of the asymmetrical current is greater than a selected value, a signal is applied to the ringing circuit, halting the ringing signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.