Patent ID: 7456860

Claim:
A surveillance system, comprising: two or more pole-like main bodies installed in a surveillance area at arbitrary intervals; a light transmission signal generation unit which generates a plurality of pulse code signals in conformity to a start-stop system; a plurality of photosensors which transmit and receive a plurality of pulse-coded rays formed on the basis of the pulse code signals from this light transmission signal generation unit in different positions between the two or more main bodies; a light transmission signal control unit which sets pulse codes, which are different from each other, in all the plurality of photosensors located between the two or more main bodies; a code identification unit which identifies pulse codes of rays photodetected from outputs of these photosensors; and an alarm-processing unit which performs alarm processing on intrusion surveillance based on an output of this code identification unit; wherein a plurality of pulse-coded rays, transmitted and received between the two or more main bodies, is serially transmitted and received with a predetermined delay time; wherein signal width of the pulse-coded ray is set at 500 μs or less.