Verifying automatic line integrity diagnostic (V.A.L.I.D.) apparatus and methods for intrusion detection systems
US4804942A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 23, 1987 |
| Grant date | Feb 14, 1989 |
| Priority date | — |
| Expiry date | Nov 23, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B25/018
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
An intrusion detection loop employing an end-of-line resistor that operates with a voltage window. As the voltage window is increased, the sensitivity of the system decreases. As the window is decreased, the sensitivity of the system increases. By utilizing two comparators each having one input coupled to the loop, one can specify one voltage window when the system is disarmed and hence place the system at maximum sensitivity thereby detecting any borderline problem. In any event, the same two comparators operate to provide a different voltage window when the system is armed and hence desensitizing the loop and therefore reducing alarm probability. In this manner one can determine during the disarmed condition that the loop is operating with a borderline resistance and still employ the system in the armed condition to assure that there will be a reduced alarm probability in view of an undesirable change of the loop resistance.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.