FIBER-OPTICAL SECURITY ALARM SYSTEM Russian patent published in 1997 - IPC

FIELD: optical devices, alarm systems for protection of perimeters of areas and rooms against intruders. SUBSTANCE: device has laser light source 1, which output is connected to input of photodetector 4 through piece of multiple-mode optical fiber 2 and light beam generation unit 3. Output of photodetector is connected to input of alarm signal generator 5, which is designed as separating capacitor 6, comparator 7, pulse duration generator 9 and indicator 13. In addition alarm signal generator 5 has integrator 10, signal duration selector 8, OR gate 12 and second comparator 11. Light beam generation unit 3 is designed as tube of specific length which is made from opaque material. EFFECT: increased stability to noise, self-monitoring of optical elements. 2 cl, 2 dwg