Security system with randomly modulated probe signal
US4577184A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 23, 1983 |
| Grant date | Mar 18, 1986 |
| Priority date | — |
| Expiry date | May 23, 2003 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B29/16
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
This security system monitors a remote intrusion-sensing unit by probing it with a probe signal that is randomly modulated. The intrusion-sensing unit replies with a composite signal in which "secure" or "alarm" status information is superimposed on the random modulation of the probe signal. (The system may if desired be elaborated to accept and utilize other status information, such as "access" or "reverse correlation.") A master unit checks the correlation of the reply-signal modulation with the probe-signal modulation, and generates a special "deception" alarm if the correlation is not in accordance with an established pattern--such as positive correlation, reverse correlation, or correlation varying in some way that is systematic or otherwise determinable by the master unit. For example, the correlation requirement may be controlled by a code that is generated (even randomly) at the intrusion sensor; or the correlation check may be made insensitive to yet further superimposed variations in signal level, frequency, or delay. Such further variations may, for instance, convey specific information about conditions at the remote secured facility--such as motion, sound or vibration t…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.