The common names for an ankle monitor include electronic monitoring device, GPS tracker, ankle bracelet, tether, SCRAM bracelet, RF monitor, tag, and even LoJack. Some are official court terminology, some are regional slang, and some describe what the device actually does. Which name you hear usually tells you something about the technology inside or where the person using the word is from.
The Official Name Courts Use
The formal label used by most courts and supervising agencies is electronic monitoring device, often shortened to EMD. It’s an umbrella term that covers every type of ankle-worn tracker regardless of the technology inside. If you see “electronic monitoring device” in a court order, it isn’t telling you whether the unit uses GPS, radio frequency, or alcohol detection. It’s just naming the category.
You’ll also see the phrase location monitoring in federal paperwork. That’s the term the federal courts and probation offices use when referring to the program as a whole, including the devices themselves.
Casual and Regional Names
Ankle bracelet is probably the most common everyday name. People use it the way they’d say “wristwatch” instead of “timekeeping device.” It’s casual, it’s accurate enough, and almost everyone knows what you mean.
Tether is widely used in parts of the Midwest, especially Michigan. The word evokes being physically tied to a location, which fits how the device functions in a home-confinement setup. If you’re reading Michigan court documents or news coverage from that region, “tether” and “ankle monitor” refer to the same thing.
Tag is more common in the United Kingdom but turns up in the U.S. occasionally. It comes from the idea of being “tagged” the way an animal is tagged in a wildlife study. People on tag in Britain are people wearing an ankle monitor as a condition of release or sentence.
LoJack is slang borrowed from the car-theft recovery brand of the same name. It’s not an official term and you won’t see it in any legal document, but you’ll hear it in casual conversation.
Names That Describe the Technology
Several names tell you exactly what kind of device is involved, which matters because the three main types do very different things.
GPS Tracker or GPS Ankle Monitor
A GPS tracker, sometimes called a GPS ankle monitor, uses satellite signals, cellular towers, and Wi-Fi networks to pinpoint location around the clock and feed that data to a monitoring center.1United States Courts. Federal Location Monitoring This is the term you’ll see most often in federal court documents about location monitoring. If an officer needs to enforce exclusion zones or verify where someone has been, this is the technology they’re using.
RF Monitor
RF monitor is short for radio frequency monitor. These devices don’t track you across town. The ankle transmitter sends a constant signal to a receiver plugged in at your home, confirming whether you’re within range. When the signal drops, the supervising officer gets an alert.2United States Courts. How Location Monitoring Works RF is used for curfew enforcement and home confinement rather than detailed movement tracking.
SCRAM Bracelet
SCRAM stands for Secure Continuous Remote Alcohol Monitoring. A SCRAM bracelet doesn’t track location at all. It samples perspiration at regular intervals and measures transdermal alcohol content, then transmits the readings to a monitoring agency.3U.S. Department of Justice. Secure Continuous Remote Alcohol Monitoring Technology Evaluability Assessment You’ll hear this name most often in DUI and other alcohol-related cases. Some newer SCRAM units combine alcohol detection with GPS in one device, which can make the name a little misleading when it’s used for a hybrid unit.
Names That Describe the Purpose
A different set of names describe why the device is being worn rather than how it works.
House arrest monitor and home detention monitor both refer to a device enforcing a requirement to stay at home. The names are often used interchangeably in casual conversation, though in federal practice the two conditions aren’t identical. Home detention lets you leave for work, school, medical appointments, religious services, attorney visits, and other pre-approved activities. Home incarceration is stricter: 24-hour lockdown at your residence with exceptions only for medical emergencies and court appearances specifically approved by the judge.4United States Courts. Chapter 3 – Location Monitoring – Probation and Supervised Release So “house arrest monitor” might describe either arrangement, depending on who’s talking.
You’ll also hear pretrial monitor when the device is a condition of bail or pretrial release, and probation monitor when it’s part of a probation or supervised release sentence. These aren’t different devices. They’re the same hardware named for the stage of the case.
Immigration cases bring their own vocabulary. U.S. Immigration and Customs Enforcement uses GPS ankle monitors as part of its Alternatives to Detention program, specifically the Intensive Supervision Appearance Program, or ISAP.5ICE. Alternatives to Detention Frequently Asked Questions People in immigration proceedings sometimes refer to being “on ISAP” rather than naming the device itself.
Why the Same Device Gets Called Different Things in One Document
Courts don’t always use the same name twice. A single order might say “electronic monitoring device” in one paragraph, “location monitoring” in the next, and “GPS” further down. If you’re reading legal paperwork and aren’t sure whether two different terms refer to the same device, they almost certainly do. The variation is a drafting habit, not a signal that something has changed.
Where the name does carry real information is in what it tells you about the technology. “SCRAM” means alcohol detection. “RF” means home-range verification. “GPS” means continuous location tracking. Those distinctions matter because they tell you what the device is actually watching for, and that in turn tells you what the conditions of your release or sentence are really asking of you.
One name you shouldn’t read too much into is “ankle bracelet.” It’s accurate but unspecific. The device clipped to someone’s ankle could be any of the three main types, and figuring out which one requires looking at the court order or asking the supervising officer directly.