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US4070669A
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Anti-fraud alarm transmission line security system
Assignee: Individual
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Filing: 1976-08-27
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Granted: 1978-01-24
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Expires: 1996-08-27
Abstract
Abstract A transmitter transmits a continuous "non-alarm" signal to a monitoring center. When an alarm occurs, e.g. if a burglary takes place, the "non-alarm" signal ceases, and an alarm is indicated at the monitoring center. To prevent the "non-alarm" signal being pre-recorded and subsequently being relayed to the monitoring center to render the transmitter ineffective, the monitoring center transmits random trap pulses having a carrier frequency different from the "non-alarm" signal. If the monitoring center detects a trap pulse at any time other than when transmitting such a pulse, an alarm is indicated.
Inventors
- 👤 Gerard A. Gautier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 05:13
CPC Classifications
H; H04; H04M; H04M11/00; H04M11/04
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
173 words
In a transmission line security system including a transmission line for carrying alarm information from at least one monitored station to a central monitor station, said alarm information being in the form of a non-alarm signal having a first frequency, permanently transmitted along said line under normal conditions and cut-off under alarm conditions; that improvement consisting of: means at said central monitor station for generating and transmitting to at least one of said monitored station a trap signal having a second frequency which is different from said first frequency and which is modulated in pseudo-random pulses; means for picking up and receiving said transmitted trap signal; means for triggering an alarm by said received trap signal; means for inhibiting said trap signal receiving means by said transmitted trap signal; said means for inhibiting said trap signal receiving means by said transmitted trap signal including means for inverting said trap signal; and, an "AND gate" for receiving on a first input said inverted trap signal and on a second input said received trap signal.
Claim 2
Dependent Claim
173 words
In a transmission line security system including a transmission line for carrying alarm information from at least one monitored station to a central monitor station, said alarm information being in the form of a non-alarm signal having a first frequency, permanently transmitted along said line under normal conditions and cut-off under alarm conditions; that improvement consisting of: means at said central monitor station for generating and transmitting to at least one of said monitored station a trap signal having a second frequency which is different from said first frequency and which is modulated in pseudo-random pulses; means for picking up and receiving said transmitted trap signal; means for triggering an alarm by said received trap signal; means for inhibiting said trap signal receiving means by said transmitted trap signal; said means for inhibiting said trap signal receiving means by said transmitted trap signal including means for inverting said trap signal; and, an "AND gate" for receiving on a first input said inverted trap signal and on a second input said received trap signal.
References Cited (Backward Citations)
US3307176A
Cited
US3934237A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-01-23 | 1981-07-25 | 1982-01-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-01-23 | 1985-07-25 | 1986-01-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-01-23 | 1989-07-25 | 1990-01-24 | $7700.00 | Window Closed / Lapsed |