GB1409658A - Flat beam intruder detection device - Google Patents

Flat beam intruder detection device

Info

Publication number
GB1409658A
GB1409658A GB5254971A GB5254971A GB1409658A GB 1409658 A GB1409658 A GB 1409658A GB 5254971 A GB5254971 A GB 5254971A GB 5254971 A GB5254971 A GB 5254971A GB 1409658 A GB1409658 A GB 1409658A
Authority
GB
United Kingdom
Prior art keywords
amplifier
amplitude
signal
change
nov
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB5254971A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shorrock Developments Ltd
Original Assignee
Shorrock Developments Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Shorrock Developments Ltd filed Critical Shorrock Developments Ltd
Priority to GB5254971A priority Critical patent/GB1409658A/en
Publication of GB1409658A publication Critical patent/GB1409658A/en
Expired legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2491—Intrusion detection systems, i.e. where the body of an intruder causes the interference with the electromagnetic field

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Burglar Alarm Systems (AREA)

Abstract

1409658 Intruder alarms SHORROCK DEVELOPMENTS Ltd 13 Nov 1972 [12 Nov 1971] 52549/71 Heading G4N An intruder detection device comprises a U.H.F. transmitter receiver arrangement having similar flat beam type directional aerials 12, 13 with overlapping radiation patterns and signal processing circuitry 15-17, 19 arranged to trigger an alrm 18 only when predetermined thresholds in respect of extent of received signal amplitude change and rate of signal amplitude change are together exceeded for a duration greater than a reference period. In operation, the transmitter 11 has its output frequency modulated by a source 10 and the modulation is recovered by Schottky diode 14 and applied via an amplifier 15 to a level detector 16. The level detector 16 detects positive or negative changes in amplitude of the received signal. The amplifier 15 is associated with a A.G.C. circuit 19 having a large time constant so that the amplifier 15 is insensitive to slow signal amplitude changes resulting from frequency drift or attenuation of the signal path by rain, snow, fog &c, Finally, the alarm 18 is activated only if the input signal rate exceeded the threshold rate determined by amplifier 15 and A.G.C. circuit 19 and if the change in amplitude was large enough to be detected by detector 16 and existed for a period determined by delay 17. When the alarm 18 is actuated, the A.G.C. time constant is reduced to readjust the mean level to which the system is sensitive. The system may use a single horizontal beam for blanket coverage or three or more vertical beams for fencing.
GB5254971A 1971-11-12 1971-11-12 Flat beam intruder detection device Expired GB1409658A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB5254971A GB1409658A (en) 1971-11-12 1971-11-12 Flat beam intruder detection device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB5254971A GB1409658A (en) 1971-11-12 1971-11-12 Flat beam intruder detection device

Publications (1)

Publication Number Publication Date
GB1409658A true GB1409658A (en) 1975-10-08

Family

ID=10464339

Family Applications (1)

Application Number Title Priority Date Filing Date
GB5254971A Expired GB1409658A (en) 1971-11-12 1971-11-12 Flat beam intruder detection device

Country Status (1)

Country Link
GB (1) GB1409658A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2506976A1 (en) * 1981-06-02 1982-12-03 Btr Sa Alarm system for protected zone containing aircraft - uses transmitters and receivers providing beam to surround aircraft and detection intrusion
EP0068050A1 (en) * 1981-06-25 1983-01-05 Shorrock Developments Limited Intruder detection apparatus
FR2709852A1 (en) * 1993-09-07 1995-03-17 Univ Limoges Method and device for detecting presence

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2506976A1 (en) * 1981-06-02 1982-12-03 Btr Sa Alarm system for protected zone containing aircraft - uses transmitters and receivers providing beam to surround aircraft and detection intrusion
EP0068050A1 (en) * 1981-06-25 1983-01-05 Shorrock Developments Limited Intruder detection apparatus
FR2709852A1 (en) * 1993-09-07 1995-03-17 Univ Limoges Method and device for detecting presence

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Legal Events

Date Code Title Description
PS Patent sealed
PCNP Patent ceased through non-payment of renewal fee