The Justice Department is experimenting with an electronic tracking program for a small number of federal parolees, attaching electronic devices to their ankles to monitor movement.

Seven parolees from Miami and four in Los Angeles have been participating in the program since Jan. 19. An additional 50 persons are to be added by April, the department said.

Under the program, offenders who do not need halfway-house services are released from prison into the community as much as six months before their parole date, the department said.

During the period of early release, parolees must be home at all times except for work, treatment programs authorized by their supervisors or worship services.

Electronic devices attached to their ankles send signals to a transmitter mounted in the parolees' home telephone to relay information to a computer, said Benjamin Baer, chairman of the U.S. Parole Commission.

When a break in contact is flashed to the computer, the monitors then try to reach the parolee. If that is unsuccessful, the parolee's probation officer investigates.

The programs costs $5 to $10 daily for each person, compared with $30 a day for a parolee released to a halfway house. About 7,000 people would be eligible if the program, which is to be evaluated in 18 months, is fully implemented, the department said.

"This program not only provides us with a low-cost alternative to a halfway house but also gives a potential alternative to incarceration for certain offenders," Baer said.

Electronic monitoring is being used increasingly by law enforcement officials nationwide.