President Richard Nixon actually wanted his conversations CAUGHT ON TAPE -- never dreaming they would ultimately lead to his resignation 40 years ago this summer. After all this time, the tapes are still yielding secrets. This morning Mark Strassmann shares a few of them:

In July of 1973, the Senate Watergate committee cornered Richard Nixon. His Oval Office had a secret recording system.

The tapes suggested a criminal conspiracy that reached the president.

June 23, 1972:

Nixon: "Play it tough. That's the way they play it and that's the way we are going to play it."

In August 1974, as impeachment loomed, Nixon resigned in disgrace.

Now, 40 years later, these same recordings are redefining Nixon's legacy.

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"Here we have this unique presidential record -- 3,700 hours," said Luke Nichter, an associate professor of history at Texas A & M. "And only around five to seven percent had ever been transcribed. For a historian, this is a gold mine."

Nichter has dusted off a library of Nixon tapes in the National Archives: "They're part private conversations and deliberations. They're the policymaking process in real time. Nixon thought he was making history, and he wanted to record that history."

Transcribing that history took Nichter 10 years. Some tapes are much easier to understand than others.

"Lot of lonely days and nights, missed date nights, that kind of thing?" asked Strassmann.

Nichter sighed: "My wife, Jennifer -- there were just some periods of time when she says, 'No Nixon.'"

In April 1971, halfway through his first term, Nixon had seven secret microphones installed in the Oval Office.

Feb. 16, 1971:

Nixon: "Mums the whole word. I will not be transcribed."

White House aide Alexander Butterfield: "Correct."

Nixon: "This is totally for, basically, to be put in the file. In my file. I don't want it in your file or Bob's or anybody else's. My file."

Butterfield: "Right."

The system was voice-activated, round-the-clock, and unprecedented.

"FDR did a little selective taping, we have John F. Kennedy's tapes during the Cuban Missile Crisis, Johnson tapes on civil rights, and all that are valuable," said professor Douglas Brinkley, who teaches history at Rice University and is a CBS News consultant. "Nixon, it's the whole kit and caboodle."

Brinkley and Nichter co-authored "The Nixon Tapes" -- seven-hundred transcribed pages of largely unheard Nixon moments.

The tapes document anti-Semitic slurs.

Feb. 1, 1972:

Nixon: "Now, Life is totally dominated by the Jews. Newsweek is totally, is owned by Jews, and dominated by them, their editorials. The New York Times, the Washington Post, are totally Jewish."

Brinkley said, "There's bigotry about people in the Third World. There's a lot of sort of barnyard cursing, unpleasant amount of backstabbing and duplicitous paranoia going on."

May 4, 1972:

Richard Nixon: "The American people are suckers. Getting to know you -- all that bulls****. They're for people to people."

The tapes cover 1971 and 1972. Foreign policy issues dominate: as Nixon conducts disarmament talks with the Soviet Union and opens the door to China.