Electronic monitoring in Scotland: consultation on proposals for legislation

Annex B: Current electronic monitoring technology

The tag also known as a Personal Identification Device ( PID) is usually worn around the ankle and communicates with the home monitoring unit (below) via a radio frequency ( RF) signal. The tag is robust, built with Kevlar strips and a fibre optic band running through it and it is designed to be tamper proof and also to register attempts to tamper with it. It is important to note though that it is not the case that it could not be removed by an offender. It is designed so that if it needs to be removed, for medical reasons for example, it can be cut. It is designed to be robust so that such an action to cut or remove the tag could not be taken accidently and the tag will accurately register if such an attempt, successful or otherwise is made. The information the tag sends to the monitoring unit provides information about a person's movements within an agreed location. The locational information is essentially binary though: in other words in terms of "location" it can only indicate whether the tag is present (or is not present) within the range of the home monitoring unit. The tag only "communicates" with the monitoring unit and it is the monitoring unit that sends the information back to the monitoring company. This means that the two pieces of equipment need to be within range of each other in order for locational information (such as whether the tag is present) or other information (such as whether the tag has been tampered with) to be registered by the monitoring unit.

The home monitoring unit is a data collection and communication device which is placed at the restricted location and continuously collects and stores data from signals sent by the tag. It has a signal detecting range which can be set to cover the size of most domestic dwellings. It then passes the data collected to a central computer at a monitoring centre via either a landline or mobile phone network. The monitoring unit has battery backup so it can continue to operate and can continue to store events even if the power or communications routes are interrupted. These recorded events can then be communicated back to the monitoring centre once the power or communications link is restored. The events communicated back to the monitoring centre are acted upon by the monitoring company. The monitoring unit has 'tamper and tilt' recognition technology that will register and communicate any attempts to tamper with the box or move its location. The monitoring unit has a phone which can allow the company to call the restricted location to speak to the offender or can allow the offender to call the monitoring company. The monitoring company then report on how each order is being monitored (compliance or non-compliance) back to the supervising officer or authorising agency (Scottish Courts, Scottish Prison Service, etc.) who will decide on the most appropriate action to be taken in response to each case.