Eleven years ago, when law enforcement agencies throughout the country were stocking up on sophisticated devices to catch speeding motorists, an electronics expert in Ohio began manufacturing a small black box that warned a driver when he was being tracked by police radar.

Dale T. Smith called his black box a "fuzzbuster." It was a name and a piece of equipment that caught on in a big way, so much that Smith's company, Electrolert Inc., sold more than 1 million "fuzzbusters" last year at $80 each.

But it was also a name and a piece of equipment that policemen grew to despise, so much that they began lobbying state legislatures to ban them. That effort came to Maryland yesterday when the Senate Constitutional and Public Law Committee heard testimony on a bill that would prohibit the nonofficial use of radar detection devices in the state.

"I can see no reason for these (fuzzbusters) other than to try to break the law," said state Sen. Robert Stroble (R-Baltimore County), the bill's chief sponsor. "We shouldn't encourage people to come up with things that cirumvent the law."

That as the sum and substance of the testimony against "fuzzbusters," offered by Stroble and various law enforcement officials. The black boxes have only one purposes, they said, and that was to help drivers speed without being caught by police radar. "It is a dangerous and growing phenomenon," said Capt. Neile Williams of the Maryland State Police. "From what we've heard, the manufacturers can't supply them sufficiently for the demand."

According to several witnesses, Virginia is the only state that currently prohibits the use of radar detection devices. The Virginia law has been challenged in court on two grounds - it makes a presumption of guilt on the part of the "fuzzbuster" owner and it regulates in effect the radio airwaves, something that only the Federal Communications Commission is allowed to do.

"Everyone makes the presumption that is you have a fuzzbuster you're a chronic speeder," said Smith, who traveled to Annapolis from Troy, Ohio, to testify against the bill. "Most of our users are professional truck drivers. They don't use them to speed, they use them to protect their livelihood. Our studies show that these people drive eight times as much as the average driver and have an 11 times better accident record."

Smith, with an obvious economic stake in the defeat of the bill, said he was first motivated to manufacture the "fuzzbuster" after he was arrested for speeding in Ohio in 1966. "The truck in front of me was speeding, but that truck pulled off on an exit before the trooper got to me," Smith claimed. "The radar equipment can't make distinctions like that. It can't pick out one speeding vehicle among a group of vehicles."

Thousands of truckers and other motorists, Smith claimed, use the "fuzzbuster" to protect themselves from that sort of incident. "You can't be trapped by unreliable radar if you know it's in the area," he claimed.

Smith presented the committee with a packet of letters written to Overdrive Magazine complaining about the way Virginia state troopers deal with "fuzzbusters." One letter from trucker Gregg Steel of St. Mary, pa., read in part:

"I was fully aware of the Virginia law. Therefore, I took precautions at the Virginia border and removed my fuzzbuster from the windshield before I'd get caught. Don't work that way. I think the cops in Virginia can smell a fuzzbuster and are that greedy that they'd spend one hour to find it. That's how long it took him to find mine."

Smith and other witnesses noted that the Virginia law has resulted in some nasty - sometimes violent - confrontations between troopers and truckers over the years. A jurist in Michigan noted that one reason for such confrontations may come from the name "fuzzbusters." Judge Ronald J. Taylor, in an opinion striking down a state law similar to the one proposed for Maryland, wrote that the "name fuzzbuster" would appear to be deliberately antagonistic to the police and thereby promotes to some degree, perhaps, alleged righteous antagonism in return. Therefore, if the name were otherwise, perhaps we would not be here today."