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Case Studies Security
Ankle Monitor

Powering Parole Monitoring

An early look at data-driven policing

For decades, law enforcement have supervised parolees with electronic tracking devices embedded in ankle bracelets. These systems have increasingly been adopted with more than 120,000 convicted criminal offenders wearing ankle bracelets in 2015, up from 53,000 in 2005.

MTSI was one of the early designers of the technology when assisting a Dallas-based company developing an alternative to overcrowded and expensive jails. The ankle-monitoring device needed to relay signals while being comfortable, reliable and tamper resistant. To make the device discrete, it also had to fit under a pant leg — and it needed a long battery life and be waterproof.

The data from the monitoring devices also needed to be captured with a variety of computers at the time including MS-DOS and Unix operating systems. But law enforcements agencies were busy keying in the file formats and reports by hand for their accounting purposes. High labor costs resulted.

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The new device needed to be more efficient at transmitting data, especially in the event of a parolee violating the terms of their parole. Information had to be collected, sorted, and analyzed against the parolee’s personal schedule as set by each parole officer. Violations needed to be sent immediately and directly to the parole officer.


MTSI engineers specified a local area network (LAN) file server computer and network operating system (NOS). An existing computer was reformatted with the new network operating system and tied the workstations together via the LAN. Individual off-­the-shelf equipment was integrated into a complete system.

The software automatically re­solved the unique file system formats for four diff­erent monitoring devices into a common database. 

Moreover, the software kept track of hundreds of parolees and their parole officers, placed automatic phone calls to follow up on potential violations, and kept a log of events that parole officers would use in their weekly reports.

The quantitative analysis showed significant decreases in the failure rate for all groups of offenders, and the decreases were similar for all age groups.

– Department of Justice

Re-keying of data was eliminated, cutting staff at peak times from 15 monitoring personnel to three. Reports were automatically formatted and sent on a violation on a daily or weekly basis depending upon the terms of the parole. The device had controls for the automatic dialing of the phone system, a video tape recorder, and a video telephone. MTSI also developed a radio transmitter that was small in size, light in weight and secure against tampering.  

Extensive use of surface mount technology (SMT) was required.