Apparatus and method for incoming call detection and alarm circuitry for cellular telephones
US5640441A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 8, 1995 |
| Grant date | Jun 17, 1997 |
| Priority date | — |
| Expiry date | May 8, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M19/047
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An apparatus for use with a cellular telephone to indicate an incoming telephone call to a user includes a cellular telephone battery pack has a circuit that generates a voltage signal with a value representative of the current being drawn from the battery by the operation of the cellular telephone. A status determination circuit monitors the voltage signal and generates a waiting for call state signal whenever the value of the voltage signal decreases from a first selected higher value to a first selected lower value for a first preselected period of time. An incoming call detection circuit whenever the waiting for call state signal is present and either the voltage signal increases from a second selected lower value to a second selected higher value and remains at or above the second selected higher value for a second preselected period of time, or the current goes from a lower preselected current value to a higher preselected current value and remains at or above the higher current value for a third preselected period of time. An alarm is operative upon receipt of the alarm start signal for indicating an incoming call to a user. Also a cutoff circuit monitors the voltage of the …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.