Ira Keiser sports a red-tinted wig and wears a set of suspendersalong with his belt, just in case. He is the security-minded type.

For nearly 10 years, the 71-year-old curmudgeon with a knack for electronics has fretted about possible break-ins at the red brick courthouse where he works as building superintendent.

"He is security-conscious to the point it is an obsession," said James W. Mulford, probation officer at the Ayer District Court. State troopers thought so too when they heard conversations from other parts of the building leaking from Keiser's office.

Authorities say security concerns pressed so heavily on Keiser's brow that he bugged most of the 27 rooms in the building with homemade eavesdropping devices. Police say he even strung an antenna wire past the window of the presiding judge's chambers.

But now the security tables have turned on Keiser. The police, armed with a nine-court indictmentfor illegal wiretapping handed down by a grand jury Tuesday, are looking for him. An arrest, police say, is imminent.

"He is a bit of an eccentric," said co-worker Mulford.

But state police detective Lt. George E. McGarrity describes the fugitive janitor as a "veru spry, energetic, tireless and a very clever gentleman.

"He was so clever that in our opinion he built equipment . . . [with a] capacity to transmit conversations in the building to his office," McGarrity said.

"How the informationwas being used in another question we still have to answer," he said. "But we have to treat it as a very serious situation. It was a substantial violation of others' rights that goes to the very cornerstone of thecriminal justice system."

Brandishing a court order last Wednesday, a search party of 15 state and local police officers, assistant district attorneys and electronics experts from the First Security Service Corp. of Boston combed the courthouse for 12 hours and turned up enough secret surveillance equipment to fill three large cardboard boxes.

They found tape recorders, transmitters, transformers, battery packs, receiving devices, wire and tiny microphones the size of coat buttons. Carted off too were 28 cassette tapes and a stack of how-to electronics manuals sitting on Keiser's desk.

"Some of the devices were so small and so portablethat there was no place in the courthouse that could not have been bugged," said J. William Codinha, first assistant district attorney for Middlesex County.

Investigators uncovered devices in telephone booths, offices, courtrooms and inside desk calenders.

"We suspect [the bugging] was going on for a substantial amount of time," Codinha said.

Receiverswere found in Keiser's office.

"They were all pretty simple devices. Anyone could have put them together," said McGarrity. "But then I'd saythey were pretty sophisticated for a 71-year-old man."

However, Keiser's fellow workers point out that he had a way with electrical gadgets. "He would repair anybody's radio in the building. He was really gook like that," Mulford said.

Reportedly, Keiser once worked as a repairman at Nike missile sites throughout New England.

Evidence of the bugging devices was originally uncovered by Assistant District Attorney Dante Demichaelis, who is prosecuting a case involving two Green Berets at nearby Fort Devens in which one soldier allegedly paid the other man $5,000 to kill his wife.

Authorities say there is little evidence that the case is connected to the wiretaps.

"We just won't know much of anything untilwe listen to those tapes," said First Assistant District Attorney Codinha.

McGarrity says Keiser is the only suspect in the bizarre bugging.

But Codinha has ordered his investigators to interview all of the more than 100 persons who work at the little courthouse 30 miles west of Boston to learn who may have had access to the dozens of homemade bugging devices. CAPTION: Picture, Massachusetts State Police officer Rod Hendrigan displays seized electronic gear. AP