This is going to be a classy inauguration with a very strict dress code. So strict it is going to cause some difficulties for the telephone repair technicians who have installed all the necessary additional telephone systems in the hotels and ballrooms around town. Don't be surprised if you are at a gala or ball and see a telephone technician in formal attire coming in to work on a misbehaving telephone. As Tom Farrah, an AT&T Information Systems manager, said: "Getting a 42 regular tuxedo was no problem. But try finding a black velvet tool belt" . . .

Frank Sinatra's name can certainly bring results. The Vista International Hotel received a telephone call from the Convention Center yesterday ordering six corned-beef sandwiches on rolls for Sinatra, who was working through lunch on the gala. The hotel's executive chef, Uwe Toedter, called a stop to all activities in the kitchen to personally attend to the order and included kosher pickles from his private supply. The sandwiches were delivered on a sterling silver tray . . .

Sinatra will not be the emcee at Friday's gala for the vice president, as was previously announced. It will be talk show host Merv Griffin . . .

The production company Sinatra hired, Hemion and Smith, will be editing highlights from the Friday and Saturday galas and showing them Saturday night on a paid two-hour block of time on ABC-TV. And 14 corporations are spending $330,000 a minute in commercial time to pay for it . . .

Don't expect to see the Walter Mondales around town in the next few days. They have picked this weekend for some reason to go on an undisclosed vacation. Perhaps to do a little skiing, one source said. And who would blame them? . . .

The Old Original Bookbinders of Philadelphia will be in town over inaugural weekend handing out about 300 box lunches around town. The restaurant says it is the first time it has done this since the 1952 Eisenhower inaugural. For Sinatra, Philadelphia publisher Walter Annenberg and a few other celebrities, they will deliver cheesecakes . . .