Electronic audio signalling device for telephones
US4157459A · kind A · utility
10Cited by
4References
7Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Oct 19, 1977 |
| Grant date | Jun 5, 1979 |
| Priority date | — |
| Expiry date | Oct 19, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M19/04
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A signalling device to be substituted for the usual electromechanical ringer of a telephone, either as a replacement for that ringer in existing telephone instruments or as a part of the original manufactured instrument. It includes solid-state circuitry for eliminating noise pulses and an electronic oscillator circuit which will operate effectively on a minimum current supply along with a mechanical arrangement of components to obtain a compact unit with a folded horn type acoustical loading system and adjustable volume control.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.