Digital composite tone alerting
US4972466A · kind A · utility
4Cited by
5References
3Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Sep 12, 1989 |
| Grant date | Nov 20, 1990 |
| Priority date | — |
| Expiry date | Sep 12, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q1/4575
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Within a digital PBX system or the like, an appartaus permits provision of digital composite tone alerting particularly suitable for piezoelectric transducers with one arbitrarily selectable tone, by means of logic circuits for latching the sign-bit in a received PCM signal that exceeds a validity threshold, and by combining the toggling sign-bit with another tone to yield the composite tone.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.