Norton Frickey realized that he must have hit on a profitable idea when law firms began calling to offer him money.

"You see, lawyers, they generally want to be on the receiving end of funds," the amiable Frickey observed last week. "That's the nature of that beast. So when it struck me that I had these lawyers calling my office wanting to pay me money, I knew that I had come up with an idea of some merit."

The idea--a ho-hum notion in most business circles but somewhat revolutionary in the legal world--is television advertising. After a modest start four years ago with some low-key, 30-second spots for his own small law firm here, Frickey has emerged as the nation's leading producer of TV ads promoting the services of personal-injury lawyers.

It all started when Frickey began advertising on Colorado television stations to beef up his own personal-injury case load. About two years ago, visiting lawyers who saw the ads--"lawyers have lots of money, you know," Frickey explains, "and they go skiing at Aspen"--began calling up to ask if they could buy the ads for their media markets.

Gradually, Frickey branched into the advertising business, with highly lucrative results.

Today about 100 law firms from coast to coast are paying, at a standard fee of $10,000 per year, for Frickey's service, an "ad-of-the-month-club" operation in which lawyers receive new ads every few weeks plus advice on how best to use them. After a seminar for potential customers here last week, Frickey's advertising firm, Network Affiliates Inc., expected to land another dozen customers.

As his service has snowballed, Frickey's plans have grown, too. His ads now feature top celebrities. The current star is football's John Madden. Next year, if negotiations succeed, the lawyers' pitch man will be Raymond Burr, who played television's best-known attorney: Perry Mason. Using those names, Frickey hopes to add more than 50 other law firms to his network.

Frickey already serves lawyers in nearly every major media market. With national saturation, he plans soon to start something fairly close to a national personal-injury law firm.

His ads will begin to mention the "Association of Personal Injury Lawyers," consisting of his advertising clients. The ads will include an 800 telephone number that can be called for a referral to the nearest Frickey-network law firm.

All this has come about despite resentment, and often heated opposition, from the legal establishment in many states. The Iowa Bar Association went to court and obtained an injunction stopping a Des Moines firm from running the Frickey ads. His customers in some other states have suffered everything from nasty remarks to ostracism from lawyers who believe advertising is beneath their profession.

Frickey responds to such opposition with a solid strain of populism that he acquired growing up during the Great Depression on the Kansas prairie. "Your silk-stocking lawyers, they don't want to see little firms do well," he snorts. "They think lawyers are just for your affluent people. We represent the working stiff, the shot-and-a-beer guy who doesn't have a lawyer. A lot of your high-class lawyers think it's pretty tacky to seek out those people."

To reach that target audience, Frickey's advertising program follows two rules.

First the 30-second spots center on a "slice-of-life situation" just as ads for beer, detergents and hamburgers do. Reflecting the target audience, perhaps, the most successful of the ads focus on bowling, softball and billiards. An ad portraying two affluent joggers was a flop, Frickey says. "Nobody calls after that one."

Frickey's advertising clients can always tell which ads work because of another basic rule: The commercials always run during working hours.

"What happens is people see the ad and immediately call the lawyer," says Jim Jorgensen, who works here buying TV time for all Frickey clients. "The lawyer has to be in the office to get the call.

"Anyway, a guy that's hurt bad enough to require the services of a lawyer is either sitting around home or lying in a hospital all day, and he's watching daytime TV," Jorgensen adds.

The results of Frickey's 30-second melodramas can themselves be dramatic. A lawyer in Tacoma, Wash., reported 126 phone calls within an hour after the first John Madden commercial aired last month.

Charles Shanker, a lawyer on K Street NW, who is Frickey's client in the Washington, D.C. market, said that the advertisements "had quite an impact" when he started them last year. "I would like get 10 to 15 phone calls a day, maybe 20," Shanker says. "Out of those I would probably get 10 or more reasonable cases to try."

However, Shanker had a problem with the ads. "It was the cash flow," he explains. Buying 12 $100 spots each week, Shanker says he was paying "maybe $3,000, $4,000 a month on advertising, plus Mr. Frickey's fee. That brought in cases, but my cases won't mature for 18 months or two years. So they didn't bring in the money to pay for the advertising right away."

Shanker, who runs a one-man firm, says the advertising program is probably better suited to a firm of half a dozen or more lawyers that can expand to handle the increased caseload.

That's what happened to the patriarch, Norton Frickey. When he began advertising in 1979 he had a two-person law office handling about 80 cases per year. Today his legal practice employs 20 and gets 120 new clients each month.

But that growth is small potatoes compared to the blossoming of Frickey's advertising business, which has become a million dollar-plus operation in less than two years. He already has his own producer, time buyer, marketing experts and studio here, and all prospects suggest more growth to come.