Ankle monitor
An ankle monitor is a device that individuals under house arrest
House arrest
In justice and law, house arrest is a measure by which a person is confined by the authorities to his or her residence. Travel is usually restricted, if allowed at all...

 are often required to wear. At timed intervals, the ankle monitor sends a radio frequency
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

 signal containing location and other information to a receiver. If an offender moves outside of an allowed range, the police will be notified. Ankle monitors are designed to be tamper-resistant
Tamper resistance
Tamper resistance is resistance to tampering by either the normal users of a product, package, or system or others with physical access to it. There are many reasons for employing tamper resistance....

 and can often alert police to tampering attempts.

The most common configuration is a radio-frequency transmitter unit that sends a signal to a fixed location receiving unit in the offender's residence. The residence unit uses either a land line or a cellular network
Cellular network
A cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell site or base station. When joined together these cells provide radio coverage over a wide geographic area...

 to relay information to a service center computer. If the offender is not at the residence at times stipulated, 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, but the offender also carries a GPS cell phone unit that receives a signal from the ankle unit, or both functions may be combined into one ankle unit.

Electronic monitoring was originally developed by a small group of researchers at Harvard University in the 1960s, headed by R. Kirkland Schwitzgebel and his twin brother, Robert Schwitzgebel (family name shortened to "Gable" in 1983). In 1983, Judge Jack Love in Albuquerque, New Mexico, inspired by a Spider-Man comic strip, initiated the first judicially sanctioned program using monitoring devices. These were produced by Michael T. Goss, a former Honeywell
Honeywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....

 computer sales representative. Shortly thereafter, programs began in Florida using a cuff invented by Thomas Moody. Within six years, at least 16 manufacturers were listed in the Journal of Offender Monitoring. In 2007, an estimated 130,000 units were deployed daily in the United States. They also gained popularity in the United Kingdom, but adoption in the rest of the EU was a little slower. A collection of early equipment and a written summary, with photographs, of the history of commercial devices in the United States is housed at the Archives of the History of American Psychology, University of Akron, Akron, Ohio, USA.

The effectiveness of monitoring in reducing crime is uncertain. There is probably a reduction of criminal behavior while the offender is actually being monitored, however a thorough and comprehensive review of research literature has indicated that, over a period of three years, monitoring did not reduce crime more than other prison diversion programs. The inventors, Kirkland and Robert Gable, who are now emeritus Professors of Psychology at California Lutheran University
California Lutheran University
California Lutheran University is a university of the Evangelical Lutheran Church in America located in Thousand Oaks, California.-Mission statement:The University's mission statement is as follows:...

 and the Claremont Graduate University
Claremont Graduate University
Claremont Graduate University is a private, all-graduate research university located in Claremont, California, a city east of downtown Los Angeles...

, have been strongly advocating the use of positive incentives in monitoring programs.

Continuous transdermal alcohol monitoring is capable of monitoring alcohol consumption in individuals. The National Highway Traffic Safety Administration
National Highway Traffic Safety Administration
The National Highway Traffic Safety Administration is an agency of the Executive Branch of the U.S. government, part of the Department of Transportation...

 produced a favorable report on the use of electronic monitoring of DUI
DUI is a three letter acronym that may stand for:* Driving under the influence * Democratic Union for Integration — the largest ethnic Albanian party in the Republic of Macedonia* Data Use Identifier...

offenders, with lower recidivism rates and less cost compared to jail.
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