Telephone ringer circuit
US4658419A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 22, 1981 |
| Grant date | Apr 14, 1987 |
| Priority date | — |
| Expiry date | Jul 22, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M19/04
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A telephone ringer circuit having a ring signal detection network serving to detect ring signals utilizing an R-C network and operating in conjunction with a threshold responsive detection device. Upon the detection of a valid ring signal, the resistance component of the R-C network is by-passed to permit low impedance passage of electrical energy into the ringing components of the circuit. Drive for a piezoelectric crystal driven audio output is provided by two push-pull amplification stages, configured as integrators, so as to effect crystal drive with trapezoidal shaped waveforms wherein high harmonics are not evolved. Improved loudness and sound quality are achieved with the circuit.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.