In significant ways, the regulatory policies of the Federal Communications Commission and the technological structure of the telecommunications and broadcasting industries have changed dramatically during Charles Ferris' 3 1/2-year tenure as FCC chairman.

It may be too early to judge the impact of what the FCC has done under Ferris, who leaves the agency in April. But it is clear that the deregulatory thrust of the FCC, which has loosened its own hold over significant parts of the cable, satellite, telephone and radio industries, will be remembered as vital to the emergence of a new wave of communications technology.

Despised by most segments of the radio and television business, practically worshipped by the booming cable television industry and viewed with a degree of curiosity by FCC staff members, Ferris undoubtedly will be remembered as bringing on a time of change.

Rarely has an agency chairman in recent memory run a regulatory panel with such a firm -- even domineering, say commission staff members -- hand as Charles Ferris.

FCC bureau chiefs, knowing that firmness well, have given Ferris as a going-away present a picture of himself, sword in hand, astride a Mongolian horse on the Great Wall of China. The caption reads: "To our leader as we will always remember him."

"We've accomplished a great deal more than I ever thought I'd be able to," Ferris said in a recent interview. "We've changed the whole institution of the FCC as to how decisions are made. It's sort of unreal, but I almost wish I could cite disappointments in this job, because in every other one I've had, I always had them.

But to run through the major policy accomplishments of the Ferris' administration at FCC is to list a series of decisions that go to the heart of the communications revolution.

The agency's "Computer II" decision lifted historic restrictions on American Telephone & Telegraph Co.'s ability to offer data processing services, setting the stage for the further merging of the telephone and computer industries as well as adding to the ongoing policy debate about the future of the Bell System.

The elimination of key restrictions about cable television such as those that governed the industry's programming, recordkeeping and ability to utilize satellites, for example, provided the groundwork for the current cable television boom.

And local broadcasters greeted with glee with FCC's decision to deregulate significant portions of the radio industry, eliminating what were universally viewed in the industry as burdensome, costly paperwork requirements.

Although appeals courts have yet to rule on challenges to key portions of that legacy of significant policy decisions, Ferris will leave the FCC have made an unmistakable imprint on every facet of how the American public relates to the telephone and the television. "We're making judgments here that will affect the structure of society 20 or 30 years from now," Ferris said.

Some of those developments were as much a result of technological change as they were a product of regulatory policy, Ferris points out. But many were based on a deregulatory philosophy ultimately shared by at least four members of the seven-member Fcc.

But, at the same time, local broadcasters seem to view Ferris with an unprecedented degree of animosity. "Ferris has had more impact in changing the direction of regulation than any FCC chairman in history," said one broadcasting industry source. "But broadcasters really and truly totally dislike him.

"Ferris seemed to totally ignore the kinds of local services broadcasters provide for the public. They feel they have performed public services. They don't think he ever expressed a desire to know or care about that. As a result I've never seen any one so despised. And it's a universal feeling among broadcasters, some of it without real policy reason."

Ferris says he understands their feeling. "It doesn't really bother me," he said calmly. "We have changed the whole attitude of government vis-a-vis the industry. We have opted for a more competitive environment and this does present a potential economic threat to those who aren't going to be competitive.

"Those who feel threatened probably have something to feel threatened about.

The greater majority of broadcasters have been doing their job well. Those that have been sluggish and haven't been serving their communities well, know it better than I. If their anxiety level is high, they know why themselves."

For the moment, Ferris is planning to enter private law practice here.He has recused himself from FCC policymaking until he leaves April 10, the date on which he celebrates the 20th anniversaty of service with the federal government and will become eligible for a pension. His decision to remain in office until that date has rankled some in the trade press, as has much of what Ferris has done.

But, said Ferris, the agency's one-time dependence on the reviews of the trade press no longer exists. "An agency is not captured in an overt, direct way," he said. "You capture it by capturing the informational input and the critique of policy of a particular institution. The agency needs a broader check and balance than just that."

That check and balance has come from a press and public more aware of the broad impact of key FCC decisions. "Computer II" and related decisions that have further opened competition in the telephone industry is just one example that fits into a competitive telecommunications policy with a foundation in key FCC decisions of the late 1960s and early 1970s.

"We have brought economics to the forefront, giving it equal billing with technology and the law," he said. "It is senseless for us to impose regulatory burdens on people without market power. Our common-carrier policies are some of the most significant we've adopted, and there has been an evolution of attitude on the part of many of the large players in the industry."

Ferris rejects the arguments largely put forward by AT&T that competition threatens the quality of the nation's telephone system. "That's been bandied about since 1968 and I don't think service is going to suffer one iota," he said. "People who make calls should pay for the service and I don't think everyone should have to have a plain old black telephone. Those who want to will pay for it."

What "Computer II" will do is increase the level of competition in the industry, Ferris said. But AT&T officials say the thrust of that decision -- permitting the company through a "separate subsidiary" to market nonregulated services -- and of other FCC moves -- runs counter to the efforts to break up the Bell System in the Justice Department's landmark case against AT&T. Negotiations about possible settlement of that suit are continuing.

In broadcasting, a similar laissez-faire attitude has dominated vital FCC decisions. Whether it be on encouraging the development of cable television, or revising and simplifying the radio station licensing procedure, the deregulation theme is generally consistent.

"I have well-formed ideas of where government should and shouldn't engage itself in a process," he said. "Those questions were daily confronted in Congress where I spent 15 years. We have moved, I think, dramatically away from the behavorial approach of regulation to one of a structural approach."

In endorsing the possible establishment of thousands of new radio and television stations through a different allocation of spectrum sections, Ferris says the FCC has provided the opportunity for "the first new television service in over 20 years.

"What these policies are actually providing is greater discretion and control in individual members of the public. Whether it is entertainment or hard information, the viewer and listener are going to have greater control over what he or she sees and hears, rather than that decision being made by an intermediary. The gatekeeper of the information had been determined by the structure of the broadcast industry.

Will a Reagan-appointed FCC move to wipe out or slow the competiveness that Ferris has worked to create in the industry? "I don't think what we've done can be undone if you talk in the long term, 10, 20, 30 years," he said. "Sure, you can gum the works, but the drift of technology and of policy can't be stopped.