Editing Security alarm (section)

===Electrostatic field===
Sometimes referred to as E-field,  this volumetric sensor uses [[Electroreception and electrogenesis|Electric field proximity sensing]] and can be installed on buildings, perimeters, fences, and walls. It also has the ability to be installed free-standing on dedicated poles. The system uses an electromagnetic field generator powering one wire, with another sensing wire running parallel to it. The sensing wire is connected to a signal processor that analyses amplitude change (mass of intruder), rate change (movement of intruder), and preset disturbance time (time the intruder is in the pattern). These items define the characteristics of an intruder and when all three are detected simultaneously, an alarm signal is generated.

The barrier can provide vertical protection from the ground to the height of the mounting posts (typically 4–6{{nbsp}}meters of height), depending on the number of sensor wires installed.  It is usually configured in zones of about 200 metre lengths. Electrostatic field sensors are high-security and difficult to defeat, and have high vertical detection field. However, these sensors are expensive and have short zones, which contributes to more electronics (and thus a higher cost).