NEWARK, DEL., AUG. 27 -- Maryland State Police are considering use of a windshield-mounted camera with a microphone to try to increase trooper safety by recording highway traffic stops.

The small, 1.8-pound camera, capable of filming both day and night, is activated by the trooper after a speeder or other violator is pulled over. The trooper using the audiovisual system also wears a wireless microphone to record any conversation with occupants of the car.

Although Maryland legal authorities said the device will have to be used carefully to avoid violating the state's tough wiretap laws, police said they hope it will help deter assaults on lone troopers.

Maryland State Trooper Theodore D. Wolf, on patrol by himself, was shot and killed last March during what appeared to be a routine traffic stop on Interstate 95 near Route 175 in Howard County. Two men were arrested a month later in the slaying.

Similar to monitoring devices used by some police forces elsewhere, the Silent Partner mobile audiovisual system was demonstrated during a joint drunken-driving law enforcement news conference held by Maryland, Delaware and Pennsylvania authorities here today as the Labor Day weekend approaches.

Trooper John Appleby, assigned to try out the Silent Partner device on his beat in northeast Maryland, said today he has made 60 to 65 traffic stops in the last week.

He said most motorists did not mind being filmed, but three asked him to turn off the device, which he did.

Once drivers know they're being recorded, "it acts as an attitude adjuster," said Appleby, 23, a two-year member of the force. "They become more polite. They talk nice and abide by your orders."

Appleby sees the device as discouraging belligerence and assaults. But some police officers in other jurisdictions say that if the driver is a criminal suspect and knows he is being recorded, he might assault the officer and then try to destroy the recording device.

"He could kill the trooper and then drop a match in the gas tank of his cruiser," said J.D. Coleman, spokesman for the Georgia Highway Patrol, which has about 200 audiovisual devices, called DocuCams, in its 600-car fleet. Georgia troopers do not tell drivers they're being recorded, he said.

Maryland State Police started testing and evaluating the $3,195 Silent Partner device last week and hope to decide whether to buy more for the state's 1,700 trooper force by the end of the year, officials said.

"The jury's out," police spokesman Chuck Jackson said. "It's still experimental . . . . We're looking at the concept now, not the particular equipment."

The device, made by Mobile-Vision Inc., of Kinnelon, N.J., consists of the camera, microphone, a videocassette recorder with eight-hour tapes stored in the trunk of the police cruiser and a monitoring screen mounted on the dashboard showing what is being filmed along with the date and time.

When making a traffic stop using the audiovisual monitor, a trooper parks 10 to 15 feet behind the suspect's vehicle so that the camera lens takes in the vehicle, tag number and occupants. The trooper is supposed to approach the car on foot, examine the driver's license and registration and may conduct a roadside sobriety test -- all recorded.

Those records, Jackson said, serve as a disinterested third party to protect both the trooper and the driver if there is any question about what happend during the traffic stop.

"It should enhance trooper performance," he said. And if the driver assaults the officer or tries a getaway, there will be a record of the car and tag number.

Jackson said troopers using the device are told to advise drivers as soon as they are stopped that they are being filmed and sound-recorded.

"We want full and complete candor with the public," he said. "We want them to know what we are doing."

Stuart M. Nathan, an assistant state attorney general, said Maryland's wiretap law generally prohibits recordings of conversations unless both parties agree to it.