Montgomery County officials have accelerated purchase of a sophisticated electronic security system that will include motion detector sensors around the perimeter fence of the county jail.

The action on the electronic security system, estimated to cost $100,000, comes a week after a prisoner escaped from the jail by scaling a fence. The work could begin as early as next week, said Claire Gunster-Kirby, spokeswoman for the county Department of Correction and Rehabilitation.

Kenneth F. Joppy, 27, a convicted rapist awaiting trial in Montgomery and Prince George's counties on separate sexual assault charges, escaped between 4 p.m. and midnight Dec. 19 from the jail on Seven Locks Road, officials said. Authorities were alerted to Joppy's disappearance by another inmate after Joppy had been missing for eight hours, Gunster-Kirby said.

Joppy was captured Dec. 22 as he was leaving an apartment in Columbia, county police said. Corrections officials said Joppy, who is being held in administrative isolation, escaped by hiding in a storage closet next to the jail's recreation yard. Officials said Joppy burrowed under a gate with a shovel in the closet and used a denim jacket to cover the 20-foot-high barbed-wire fence he climbed.

The jail escape heightened concerns of nearby residents and Rockville city officials. "They didn't notify people as quickly as they should have," said Mayor Douglas Duncan. "Why did it take until midnight to find out a prisoner is missing?"

Installation of the electronic security system, which had been slated for spring, was expedited because of safety fears of residents, said Graham Norton, director of the county's Department of Facilities and Services.

Norton said funding for the system was approved as an "emergency procurement," allowing the county to forgo normal bidding procedures. Instead of waiting 30 days to advertise for bidders, the county began contacting prospective contractors this week for phone bids, he said. The county hopes to select the lowest bidder today or early next week, he said.

The electronic security system will include motion sensor detectors on the perimeter fence that will trigger an alarm if an inmate attempts to dig under a gate or climb a fence, Norton said.

An internal report on the escape was submitted yesterday to department director Calvin A. Lightfoot, Gunster-Kirby said. She said officials believe the escape was the result of "human error. It looks like people did not follow procedures."

Several changes are being considered to improve security at the jail, Gunster-Kirby said. In a few weeks, guards will be given hand-held counting "clickers" to verify the number of inmates who enter and leave the jail's recreation yard, she said. And jail officials are reviewing whether an additional inmate count should be made between the 3 p.m. and midnight work shifts.

Before his escape, Joppy had last been seen in the recreation yard with about 50 inmates, jail officials said. The yard has been closed since Joppy's escape to permit officials to upgrade locks on the storage closet, shore up fencing and remove shovels and other equipment from the area, Gunster-Kirby said.