Monolithically integratable telephone circuit for supplying ringing signals to a subscriber's telephone line and for detecting an off the hook condition during ringing
US4847896A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Nov 13, 1987 |
| Grant date | Jul 11, 1989 |
| Priority date | — |
| Expiry date | Nov 13, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M19/026
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A telephone circuit, which may be monolithically integrated, for supplying ringing signals to a subscriber's telephone line and for detecting an off the hook condition during ringing, including a logic control circuit connected to exchange components which control the supply of the ringing signals and determine their rhythm. The logic control circuit is connected to a circuit for detecting direct current on the line and a current comparator for generating a signal when the value of the line current exceeds a predetermined current value. This signal is also supplied to the exchange components via a transfer circuit to inform them that an off the hook condition has taken place. The logic control circuit is connected to a timing signal generator which synchronizes its functions with times in which the ringing signal has a zero amplitude, and is connected to a signal amplifier circuit which supplies the ringing signals to the line and to the transfer circuit. When the circuit for the detection of direct current signals a probable off the hook condition, the logic control circuit disables the amplifier circuit from supplying ringing signals to the line and inhibits the transfer of any s…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.