A Michigan City woman can only imagine what might have happened had it not been for an electronic device that indicated the presence of a possible stalker.

As a result of the alert, a man is in custody and is expected to face probation violation charges and two other counts, according to his probation officer.

Michael O'Brien Jr., 41, of 3782 N. Wozniak Road, was taken into custody at 5:20 P.M. Tuesday and charged with invasion of privacy and resisting law enforcement. By court order, he was wearing The Shield, an electronic monitoring device that signals an individual's presence to a potential victim.

The Shield system consists of a receiving unit kept by the victim and a transmitter unit worn on the ankle by the accused person. Officials said that if the unit is tampered with it will indicate it on regular checking by probation authorities.

A woman who had filed complaints against O'Brien last year was alerted to his presence when he allegedly drove past her business. She quickly summoned police.

O'Brien is alleged to have fought with officers. when he was halted in the 4100 block of Franklin Street. He was charged with invasion of privacy and resisting law enforcement. Because he was on probation, he was immediately placed in jail.

O'Brien had been convicted on charges of criminal recklessness and stalking following his arrest on July 7, 1995, after he had approached the woman in the parking lot of her place of employment and pointed a pistol at her.

The arrest followed what the victim described as numerous telephone calls and letters from O'Brien, some of them threatening members of her family, that began many weeks earlier. "I finally turned a letter over to police on June 23," the victim said in a telephone interview.

The pistol pointing incident occurred just before the start of the July 4, 1995, weekend, and O'Brien was arrested and charged July 7.

The victim said that in the course of the stalking, she had repeatedly changed her telephone number, and moved three times in an effort to escape O'Brien's attentions.

"It had become a matter of danger for me, my family, and my employees," she said.

The victim said when she was in her early teens, the O'Brien family had lived a short distance from her home, but she had only a passing acquaintance with Michael O'Brien Jr. "I really didn't know him," she said.

She said many years had passed, and it wasn't until her photo and name appeared last year in a newspaper advertisement for her company that O'Brien began making phone calls and writing letters to her. She said the letters were "sick," including the names of members of her family and threats against their lives.

O'Brien's probation officer, Steve Eyrick, said the incident last Tuesday was the first time a remote receiver unit had gone off signaling a potential victim that a possible assailant was approaching.

The receiver, Eyrick said, is fully portable, somewhat larger than a video cassette and can be placed in a car or a desk. Mostly, he said, the alarms have been sounded from homes, but in this case the victim was alerted as she prepared to leave work for the day.

Eyrick said O'Brien immediately was placed in jail for 15 days, and at the end of that time he will be brought before Superior Court 4 Judge William Boklund to answer the privacy and resisting charges, and a request will be made that his one year probation be revoked.

"He is going to be in jail for almost two weeks yet, and we are examining the entire situation very closely," Eyrick said.