Security system with backup dialer
US5233640A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 11, 1991 |
| Grant date | Aug 3, 1993 |
| Priority date | — |
| Expiry date | Jan 11, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M11/04
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A security apparatus having two control and communications units adapted to monitor a system and to establish communications over a connected telephone line and to transmit an alarm upon the occurance of a predetermined event in the system. The first control and communications unit produces a characteristic signal when it is operational; and the second control and communications unit is adapted to monitor the characteristic signal produced by the first control and communications unit and to establish communications over the connected telephone line and transmit an alarm upon interruption of the characteristic signal. The characteristic signal is preferably a tone of predetermined frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.