What is an Ankle Monitor or House Arrest Ankle Bracelet ?

An ankle monitor (also known as a tether, or ankle bracelet) is a device that individuals under house arrest are required to wear in order to avoid being in Jail, ease overcrowding, or as a result of a plea bargain.  An ankle monitor is used by pretrial, as a condition or order of the court,  or parole. The Ankle monitor depending on the manufacturer will use different technologies to monitor the signals from the ankle monitor. The most common forms of technologies used are radio frequency, cellular, landline, and GPS or a combination of several of these.

At timed intervals, the ankle monitor sends a signal containing location and other information to a receiver. This range can be set from 50ft to 300ft from the base if using radio frequency. If GPS is being utilized the officer determines the range in which the offender can move around.

If an offender moves outside of an allowed range, the officer responsible will be notified. Ankle monitors are designed to be tamper-resistant and can alert authorities to removal attempts, such as cutting the fiber optic within the band causing a break in the light being detected.

The most common configuration is a GPS Cellular transmitter combination. The unit is completely self contained. It uses the cellular signal to triangulate its position and to communicate with the base computers. Some units will use the WIFI networks as well.  The GPS Satellite data is of course used to determine its position more accurately to within a few feet (20 to 30 ft) accuracy. If a cellular signal is lost the unit continues to record its GPS coordinates. Storing them for up to one week.

With the advent of cell phones and less use of landlines in homes the use of Radio Frequency units using a landline to communicate have almost become obsolete.

If an offender is not at the prescribed location such as his home, work or if he is to take a prescribed route and does not. An alert message is sent to the service center, and then relayed to the supervising probation or parole officer. GPS units are similar in design. Persons subject to a restraining order may also be subject to GPS monitoring.

A few Manufacturers of House Arrest Ankle Bracelets or Tethers include the following

BI Incorporated 


Satellite Tracking of People S.T.O.P.