One monitoring device consists of an anklet transmitter and a field monitoring device that links through existing telephone lines to a computer at the corrections office. The transmitter is lightweight and about half as thick as a pack of cigarettes. The device is worn under the sock, under the trouser leg, so the wearer can hold a job without embarrassment. The transmitter is also hermetically sealed, impervious to moisture, and capable of functioning at temperatures ranging from 40 degrees below 0 to 150 degress above 0. The strap holding the transmitter is tamper-resistant. The materials are also hypoallergenic. The transmitter signals constantly and is randomly checked by the computer throughout the evening and weekends when the offender is to be confined to the home. The computer operates on a UNIX system and is resistant to most interference by 'hackers.' Each offender's signal is unique. Michigan corrections officials expect to have 500 to 1,000 offenders using the system within the next 15 months.