The Carter/Mondale Campaign Committee people were not quite ready to receive visitors the other day. Only 10 days in thir headquarters, they wore smiles that did not yet look painted on. The elevator worked. And the posters were only in the planning stage.

The building they chose for their command post is an unpretentious chunky three-storey structure squeezed in between a pair of giant office buildings only a few blocks from the White House on the short block of Connecticut Ave. NW between H and I streets.

A wide staircase leads from the doorway to the reception desk where Madeline Phelps, a nurse who graduated from Syracuse University and now lives in Arlington, sits beneath a big 1976 poster of Carter. This is her first presidential campaign.

Julie Avery, secretary to the boss, Evan Dobelle, comes down from her third-floor "penthouse office" as she calls it. "I've always voted, but I've really only been involved in politics for the past 10 months," said Avery, a native of Washington and graduate of Marymount. "Funny, growing up in a city where politics is the major indus- try, I really never took a long look at it. But now I'm enjoying it."

Evan Dobelle runs the operation from a front office on the third floor, the newness showing in the empty book shelves and drapery rods leaning against one of the two big windows.

Dobelle, 33, twice elected mayor of Pittsfield, Mass., and more recently U.S. chief of protocol, is approaching the campaign with the eagerness of a baseball manager waiting for the season to start.

"The election is not very far away when you think of it," he said. "There's a lot to do. Of course, we are not into the 16-hours-a-day, seven-days-a-week stage yet. We have a few people out in the field. You can't get votes sitting behind a desk. We still have a very small staff but it will pick up of course, as we move along."

Once a Republican and now called a "born-again Democrat," Dobelle worked for Carter in the '76 campaign. He gave up his protocol job (to his wife, Kit) last year to become treasurer of the Democratic National Committee and since, the 1980 campaign has never been far from his mind.

Scott Wolf, a 25-year-old Brown University graduate from Pawtucket, R.I., stood in his shirt sleeves among several open cartons in the corner of his office and said he couldn't remember when he wasn't involved in politics.

Wolfe, whose job is to research issues and groups, is a veteran of the '76 campaign and has the eagerness, energy and ambition to take on another long race.

Chuck Parish from Bluffton, S.C., who began in the governor's office in Georgia in '71 and is now field director for the campaign, talks of his credentials. "I was campaign manager in Texas in '76 and someone once said it was like handling four states."

Marie Morse came up from Florida to act as an unpaid volunteer. "I worked on the '76 cmapaign and I will work on this one doing anything they want me to do," she said. "I want my children to know that I've done more than attend parent-teacher meetings."

"This is my second go-around," said Chris Murray from Darien, Conn., offering a used coffee container for an ashtray and saying, "Sec, real class, just like all the campaign headquarters."

Murray is happy to be in harness again, looking forward to the long hours and endless traveling, remembering '76 like it was yesterday, and wanting all the noise and excitement back again.

There is nothing more on the second first floors. A few empty offices, a lot of stacked cartons, telephone people working with wires, phones with a barrage of push buttons sitting on the floor.

Like every well-run campaign, the boiler room is in the basement with mailing equipment being set up and the double coffee maker half full.

In a big back room on the first floor, three people work over long ledgers checking donations and figures to keep things in order for the Federal Elections Commission.

Donna Sagemiller is comptroller of the efficient skeleton crew that will grow each week as November of 1980 nears.

A very narrow alley just wide enough to hold an antique-looking iron fire escape runs along the side of the campaign headquarters. The building, nothing much for Washington, was quiet looking in the noon rush. Inside pulses the energy that it takes to get a man elected. CAPTION: Picture, Evan Dobelle; by Margaret Thomas-The Washington Post