Electronic ringing circuit for telephone systems
US4081617A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 29, 1976 |
| Grant date | Mar 28, 1978 |
| Priority date | — |
| Expiry date | Oct 29, 1996 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M19/04
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
This invention relates to an electronic ringing circuit for telephone systems. The inventive circuit provides a dual tone output with the tones changing at a predetermined rate. The circuit consists of a rectifying circuit connected across the telephone lines which receive the normal 90VAC/20 Hz telephone ringing signals. The rectified signal is then connected to one input terminal of a voltage comparator, the other terminal of which is connected to a reference voltage source. When a ringing signal is present, the rectified signal will be greater than the voltage of the reference source so that the voltage comparator will provide an output. This output is fed to the control terminals of electronically controlled switches, and when the switches are closed, the oscillators will be grounded through frequency determining capacitors associated with the respective oscillators. In addition, associated with one of the oscillators is a second electronically controlled switch and a second frequency determining capacitor. The control terminal of the second switch is connected to the output of the other one of the oscillators. Thus, when a ringing signal comes over the telephone lines, both of…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.