High voltage message waiting circuit
US5768366A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 2, 1997 |
| Grant date | Jun 16, 1998 |
| Priority date | — |
| Expiry date | Apr 2, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M9/02
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A message waiting circuit comprised of a pair of electrical leads which carry a message waiting signal, a capacitor for storing electrical energy extracted from the message waiting signal, a transistor for allowing the capacitor to charge when the message waiting signal is within a predetermined range; a Darlington transistor for causing the capacitor to discharge; and a light emitting diode (LED) which emits light when the capacitor discharges. The flashing LED indicates that a message is waiting for a user of the telephone set associated with the message waiting circuit. Approximately ten to twenty-five message waiting circuits and associated telephone sets can be connected to a single telephone line.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.