For this type of house arrest, the offender must wear a monitor on his ankle at all times. Shaped like a small pager, the monitor is strapped to his ankle and generally includes some kind of radio frequency or Global Positioning System (GPS) technology that allows law enforcement to monitor his movements 24 hours a day. It also alerts officials if he leaves the permitted premises. The bracelet is usually waterproof. It is the criminal’s responsibility to keep the device charged and working throughout the period of house arrest. Most ankle monitors have multiple tamper-protections; if an offender tries to remove or open the device, or if it runs out of power, authorities are immediately informed. The cost of home monitoring is sometimes incurred at the expense of the violator.
Voice curfew is a cheaper alternative to an ankle monitor. In this system, the violator is not required to wear any sort of device on his person. Instead, he simply must have a phone line at the house and workplace at all times. At scheduled times, he will be called by the voice curfew company and will have to report in. Voice-detection technology is used to verify voice authenticity. The criminal is subject to random calling and must respond to these phone calls as well; if not, the voice curfew company will report this to authorities.
Because offenders are typically not allowed to consume alcohol while under house arrest, certain kinds of home-monitoring devices are designed to detect alcohol consumption. One, a type of ankle bracelet, is capable of detecting changes in an offender’s blood alcohol content (BAC) via skin contact. Another alcohol monitoring system is a picture breathalyzer; at random intervals, the offender must blow into the breathalyzer that has been installed in his house. The breathalyzer measures BAC and features a camera mount, which takes a picture during the test to ensure that it is indeed the offender who is using the breathalyzer.
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