"This is one of the better-known conspiracies," said Rep. Robert E. Bauman (R-Md.). "The fix is in."

Bauman was telling a House Post Office and Civil Service subcommittee yesterday that, whatever the merits of the $12,900-a-year pay raise recommended for members of Congress, the House should be required to vote on it. But, he said, the machinery has been rigged to let it go into effect without a vote.

A procession of witnesses demanding a House vote appeared at the hearings, whose scheduling only guaranteed that there will be no time to get the issue to the House floor before the pay raise takes effect Feb. 20. Chairman William D. Ford (D-Mich.) told them their testimony was as much participation in the legislative process as a vote.

Nothing makes members of Congress squirm more than voting on an increase in their salary. Their present pay of $44,600 a year seems enough to most people around the country who make less. "How many members would have an opportunity - not brains but opportunity - to earn as much anywhere else?" asked Rep. Edward P. Boland (D-Mass.), who is opposed to the pay raise but will accept it if it takes effect.

Freshman Rep. F. Danforth Quayle (R-Ind.) said he had a letter from a voter stating that three-fourths of the teachers in one of his towns earn less than the proposed pay raise. He said he would return his pay raise to the Tresury for the next two years. Rep. Berkley W. Bedell (D-Iowa) urged the house not to "sneak it through."

But only a miracle will prevent it taking effect without a vote. That was the point of a law passed 10 years ago to relieve members of Congress of the political anguish and fright caused by a vote to raise their salary.

The law provides that every four years a civilian commission shall recommend pay levels for members of Congress, federal judges, Cabinet officers and top civil servants in the executive branch. The President can change the figures, then sends them to Congress, and they take effect unless vetoed by either house within 30 days.

This worked in 1969, and Congress got a 42 per cent pay raise from $30,000 to $42,500. But the Senate vetoed the next round, and these top officials have received only a five per cent raise in 8 years.

President Ford sent up his pay proposals just before leaving office. The House Post Office and Civil Service Committee, to which they were referred, didnt organize to do business until last week. Chairman Robert N. C. Nix (D-Pa.) appointed an ad hoc sub-committee to conduct three days of hearings, which end today.

The House then goes on Lincoln Day recess until next Wednesday. By then it will be too late under House rules to get the issue to the House floor even in the unlikely event that the committee voted it out.

There will be another chance to vote on the pay raise several months from now, when the legislative appropriation bill goes to the House floor. That will provide the funds to pay congressional salaries next year. But history shows that once a pay raise has taken effect it is never rolled back. It would push congressional salaries below those of their staffs.

The Senate took a vote on the pay raise last week. It wasn't an up or down vote on the proposals but on a procedural motion to table - and thus kill - efforts by Sen. James B. Allen (D-Ala.) to offer a resolution of disapproval as a non-germane amendment to the Senate committee reorganization resolution. Allen lost 56 to 42.

The resolution of disapproval had been bottled up in Senate committee as it is in the House. But under looser Senate rules Allen could call it up for a Senate vote without waiting for committee action.

Sen. Strom Thurmond (R-S.C.) complained that the way it was put to a vote gave senators "a procedural out. They can say they didn't vote for a pay raise but against encumbering the committee reorganization resolution."