WASHINGTON -- Elected leaders from Maryland and Virginia are pushing plans to require electronic tracking devices be worn by sex offenders who've been released into the community, officials said.

In the District, high-tech satellite trackers are already being used to keep a constant eye on sex offenders. Dots on a computer screen allow police to track the precise movement of sex offenders wearing an electronic tracking device. This technology allows a supervising officer to know if offenders are where they're supposed to be or headed for trouble, police said.

It's the latest tool in an effort to keep sexual predators from striking again, and it's one of the most advanced systems in the region. In April 2003, the District launched a pilot program that put monitors on some 200 sex offenders.

Offenders who are closely supervised tend to do better than those who aren't, authorities said.

The offender wears an ankle bracelet that transmits regular signals to a tracking device in the offender's home. From there, data is sent to a central tracking location at a Florida call center and to law enforcement. The Florida-based company, called Pro Tech, has tracking devices in the District and 42 other states.

"Basically, the sex offenders can no longer move throughout our community with anonymity," said Richard Nimer, a Pro Tech spokesperson.

Authorities said the tracking system aims to influence the offender's behavior -- and prevent them from attacking again.

"It has a powerful psychological impact, they know at any given minute we can see their tracks on the computer, and they do feel we will come and get them if they've done something wrong," said Paul Brennan, a local court supervision representative.

The tracking system comes in two forms.

The passive system transmits a record of the offender's activities at the end of the day. The probation or parole officer can review reports in morning and possible violations are highlighted.

Meanwhile, the active system reports activity in real time, providing a minute-by-minute account of the offender's whereabouts. Also, certain areas are considered hot zones, areas off limits to the offender such as schools, day-care centers or the home of a victim. If an offender enters the zone, an immediate alert is set off.

District authorities are also in the process of testing another electronic tracking system, that’s worn like a cell phone and an ankle bracelet, police said it provides even more detailed tracking data.