A DIFFERENT STYLE. Security adviser Carlucci says he keeps no secrets from President

Millions of Americans watched on television as former national-security adviser John Poindexter described how he was responsible for the most controversial aspects of the Iran-contra affair. But one person who might have been expected to dissect these proceedings didn't: Frank Carlucci, Admiral Poindexter's successor.

``I haven't tried to draw any lessons from John Poindexter's testimony,'' Mr. Carlucci says. ``I had my own philosophy about how a national-security adviser ought to operate, when I came over here.''

Poindexter said repeatedly that he decided he could best serve President Reagan by not telling him certain things, such as where money from Iranian arms sales was going and what the contras were doing.

The new security adviser, who took office last December, says he believes in taking the opposite approach in briefing the President. If he errs, says Carlucci of himself, he ``errs on the side of giving him too much.''

Unlike members of the public, presidents are limited in the ways they get information, Carlucci says.

Locked in the White House and Camp David, surrounded by security agents, chief executives cannot just wander the halls of government looking for someone to talk to.

Aides seldom come in, put their feet up, and say, ``Look, this is what's happening,'' Carlucci says.

The national-security adviser says President Reagan has been very involved with issues such as Persian Gulf policy and security problems at the US Embassy in Moscow.

Attempting to run intelligence operations out of the National Security Council was what got Poindexter in trouble, but Carlucci reiterates that under him the NSC has no involvement in such actions.

He says he has been working since January on revising procedures for control of the covert work of the CIA and other intelligence agencies, and that the President has reviewed every current covert action, Carlucci says.

On a separate subject, the new NSC chief says the US commitment to protect Kuwaiti tankers in the Persian Gulf is not open-ended.

He says now that the tankers have been reflagged and are in effect American ships, the US government can unilaterally determine how long they need protection.

``If the threat seems to abate, there would be no need to continue the escort,'' he says.