When President Carter spoke about energy last Monday night, a national television audience got a glimpse of his desk in the Oval Office and a small sign he has placed on it. The sign bears the words of Harry S. Truman on the presidency: "The buck stops here."

During his campaign, Carter liked to identify himself with Truman, who became something of a folk hero after he left the White House. So it would be easy to see the Truman slogan, sitting there on Jimmy Carter's desk, as just another prop in the exercise of presidential symbolism.

But the evidence to date, as Carter nears his 100thday in office and has just completed a series of tough decisions, suggests that the new President not only believes in the sentiment Truman expressed but relishes it.

Despite all the talk about strong Cabinet secretaries making decisions and of a freewheeling decision-making process open to all, the Carter WHite House is not much different from its predecessors. The big decisions still come there, as they must, and when they do, the President sits down with a handful of advisers to make them.

The bigger the decision - as with his strategic arms limitation proposals to the Soviet Union and his energy package - the more likely Carter is to keep the decision-making process closely held, the better to prevent news leaks. In his abhorrence of leaks, the President shares another trait of his predecessors.

Where Carter is different, according to his aides and others who have dealt with him, is in his refusal to engage in political give-and-take with those who seek to influence him - to "wheel and deal" like a Lyndon B. Johnson - and his stiff-backed reaction to suggestions that this course or that would be politically advantageous.

If you want to get on the wrong side of Jimmy Carter on an issue, one administration official said, a guaranteed way "is to tell him that what you want is a good political thing to do."

"Oh, boy, is that true," concurred Carter, recalling his experiences with what one of his White House colleagues described as the President's apparent delight in "doing something absolutely necessary, misunderstood and unpopular."

But these traits - Carter's "the buck stops here" mentality, his refusal to "wheel and deal," at least in the tradition Washington sense - have given rise to an impression in some quarters that he is not listening, that decisions are being made in the White House without adequate consultation with the outside world, including other parts of the administration.

A labor leader compared an Oval Office session with Carter with an audience with the Pope. There is, he said, none of the "horse trading" of the Johnson or Nixon days and nary a hint from the President - who listens attentively and asks informed questions - of what the final decision will be.

A State Department official agreed. Dealing with the Carter White House he said, " makes you work like a dog if you're in the executive branch. You can't really rely on knowing where he's going to come down, so you have to put it all on paper and think it all through."

Describing a meeting with officials of the Office of Management and Budget, Wallace T. Sansone, director of policy and planning at the Maritime Administration, said: "They're just like a vacuum cleaner over there. They suck it all in and don't give out anything."

These impressions may result in part from the clash between campaign rhetoric and reality. Carter spoke so often during the campaign about "openness in govenment" that he may have led some people to think that they would be sitting at his right hand when the fate of their issue or project was decided.

That, at least, is the view of the President's defenders in the White House who say that lack of feedback from the White House does not amount to lack of consultation or mean that Carter is not influenced by other than his immediate staff.

"What they really mean is that they want to run the thing," said one White House aide of those who complain about lack of consultation and feedback.

"You can have an open government," he added, "but that doesn't mean you have to take the position of everybody who walks in the door."

But Carter aides also concede that some mistakes have been made in the early days of Carter's evolving presidential decision-making process, that maybe in some cases not enough people were invited inside the door, or at least not soon enough.

Once conspicuous example was the President's decision to abandon the $50-per-son tax rebate portion of his economic stimulus package, an apparent example of "the buck stops here" mentality at work.

From all accounts, it was Carter who first raised doubts about the rebate, although they were shared by other powerful figures in the administration, inlcuding OMB Director Bert Lance.

Carter convened a meeting on the subject at which some of his confidants - vice President Mondale, political adviser Hamilton Jordan, domestic policy chief Stuart Eizenstat - argued for retaining the rebate.

But no final decision was made at that meeting, so at noon that day one of the participants, Treasury Secretary W. Michael Blumenthal, gave a speech in support of the rebate. And on Capitol Hill lobbyists for the AFL-CIO, which had lately and reluctantly been persuaded to work for the rebate, continued to do just that.

The next day the President announced his decision to withdraw the rebate, much to the displeasure and embarrasment of his supporters who were not let in on his change of mind,

"Hell, I'm up in Connecticut the same day giving a press conference on how essential this stimulus package was," said House Budget Committee Chairman Robert N. Giaimo (D-Conn.).

When it came time to make his most important domestic decisions, on the energy package behind which he has thrown his prestige, Carter did played a tendency to play it even closer to the vest than usual. Until nearly the end, the energy package was shaped largely by the President and his chief energy adviser, James R.Schlesinger Jr.

It was not until Jordan pushed for it that the process was opened especially to some of Carter's economic advisers who were concerned about the energy proposals' impact on the economy. Another freewheeling meeting was called and while it did not significantly alter the energy package, it is considered in retrospect at the White House to have been a healthy exercise.

"We didn't o that with the minimum wage about I wish we had," said one Carter aide, at the same time cautioning that the President's decision to recommend much less than what organized labour sought probably would not have been different.

Thope around the President say they think he will learn from whatever mistakes have been made during these three months, that complaints about lack of consultation and a closed decision-making process will diminish. But they also caution against any notion that Carter didn't mean it during the campaign when he said he intended to be a strong President.

The sign on the big wooden desk in the Oval Office is not likely to be removed.