초록 ▼

An intrusion detection system of the type using cables arranged along a perimeter to be protected and sensing changes in the electrical field around the cables caused by the presence of an intruder. The cables are divided into sections or blocks and typically only one of the sections is energized at

An intrusion detection system of the type using cables arranged along a perimeter to be protected and sensing changes in the electrical field around the cables caused by the presence of an intruder. The cables are divided into sections or blocks and typically only one of the sections is energized at any time. The variations caused by an intruder at the selected sections are transmitted through the intervening section to the receiver portion of a transceiver located at one end of the cables. This indicates in which section intrusion has occurred. The system uses continuous wave excitation whereby the expense and complexity of high speed switching and timing of r.f. signals are avoided.

대표청구항 ▼

A perimeter intrusion detection system, comprising: first and second cables arranged along the perimeter and connected to a transceiver, each cable having a plurality of sections separated by switching units, each section defining a pair of adjacent paths, one path being a well-shielded path and the

A perimeter intrusion detection system, comprising: first and second cables arranged along the perimeter and connected to a transceiver, each cable having a plurality of sections separated by switching units, each section defining a pair of adjacent paths, one path being a well-shielded path and the other being an incompletely shielded path adapted to couple to an external field, each switching unit being adapted to connect the incompletely shielded path of a selected single section of the first cable and the incompletely shielded path of a selected adjacent section of the second cable to said transceiver via the well-shielded paths of the intervening sections whereby the pair of selected sections are coupled by the external field and variations in the coupling detected at the transceiver indicate the presence of an intruder in the are of the selected sections.