Outside the lobby of The Washington Post's downtown office building stands a red and gold contraption.

It looks like a monument to the late Rube Goldberg, whose zany cartoons satirized America's preoccupation with technology and attracted popular attention as well as a Pultizer prize when published in the press.

In the manner of roadside historical markers, a sign tells tourists and visitors that they are looking at a "Linotype Model 31 line-casting machine," manufactured by the Mergenthaler Linotype. It goes on:

"This machine, representive of the very heard of the newspaper production process,saw more than a quarter of a century's service molding lines of type from molten metal in The Post's composing room."

The past tense is a key element in the description because Linotype machines are on the way out.

Publishing of newspapers is a manufacturing process that dates back to the mid-15th Century when the Chinese first constructed moveable type and Johann Gutenberg introduced such type in Europe. It was a real breakthrough in technology, permitting the piecing together of hundreds of letters into a single page and wedged into a wood frame.

After impressions were made from that frame, the pieces could be used again and again for additional pages. The age of mass communications had started.

At first, the movable type and flat printing presses were used primarily for books and pamphlets but in the early 1600s, weekly newspapers began to be published in Germany, Holland and Belgium.

It was not until 1702 that the first English-language daily newspaper was founded in London. An iron press invented in 1798 permitted a sharp increase in the number of papers that could be printed every hour and in 1840 a German process for making paper from wood pulp led to the initial mass marketing in publishing. A "rotary" press was invented in 1846, allowing another sharp increase in the number of papers that could be produced every hour: another press invention permitted printing on both sides of a continuous roll of paper.

But the industrial revolution truly came to newspaper publication when Ottmar Mergenthaler filed a patent in 1885 for the first linotype machine, which tripled the speed of typesetting when introduced in the composing rooms of newspapers.

Workers sat before the machines, typing out reporters' stories line by line into rectangualr pieces of metal; instead of piecing together thousands of individual letters for one edition, workers began piecing together entire lines, stacked together to form columns of type.

Within a 40-year span, meanwhile, transatlantic cables were constructed, allowing up - to - the - minute news reports; the telephone was invented, adding to the speed of information exchange; electric lights were invented, stimulating after-dinner readership: and typewriters were invented, speeding the process of writing.

The newspaper became big business and by 1900 there were 2,326 dailies in this country alone, about six times the number during the Civil War. Such pioneers in mass marketing as Joseph Pulitzer and William Randolph Hearst helped circulation soar by adding new elements of human interest, gossip, crusades and cartoons.

Until recent years, however, there had been no significant changes in the technology by which newspapers were produced. Over a span of the years that included introduction of automobiles, airplanes, nuclear weapons and flights to the moon, newspapers reported these events with a process basically invented in 1450 and only refined in subsequent years with better presses and Mergenthaler's lines of type.

While newspapers were a late 19th Century example of dvanced technology and early automation, in the years following World War II, it became clear that newspaper factories were using more old fashioned and cumbersome production processes than any other major American industry.

Today, however, the newspaper business is experiencing a technological revolution. Although most pages in any week's editions of The Washington Post or New York Times today are printed in a process not much changed from conditions that existed in the 1890s, that will not be the case several years from now.

The technologies of space-age electronics and modern photography already have been introduced at many of the nation's smaller newspapers and some big dailies as well.The Wall Street Journal, for example, is printed at 10 plants aross the country: in some cases, material presses by satellite.

Up until this decade, most major newspaper publishing companies were cautious in studying the new technologies being offered to them. And there was a good reason: Huge capital investments in existing machinery.

Now, perfection of some production processes combined with the ravages of a deep recession and high inflation have caused most publishers to declare true faith in the new technology.

There have been two major developments: Offset printing and cold type, terms not widely known outside the publishing business.

Offset printing accually is an older process but it was captured by weekly newspaper publishers in the 1950s as they searched for a cheaper process and one that enhanced graphic and photographic reproduction.

In the offset process, an image of a newspaper page on a photo-sensitive plate is transferred (or offset) to a rubber blanket and thereafter to the surface of paper, with ink attracted only to that portion of the page representing type or graphics.

Introduction of offset printing led to development of the other new technology, cold type. Use of Linotype machines to cast lines of type in "hot" metal became unnecessary when all that was needed was a simple photograph of a complete newspaper page.

Various companies experimented and developed photographic omposition processes by which type could be sprayed out on photographic paper, or sliced and pasted down on big sheets of paper. Headlines and photographs, and advertisements similarly were produced for pasting down. When complete, a photo is taken of the finished page and it is transformed into a printing plate for the rotary presses.

Today, these two processes are sweeping the industry, in combination with computers and video terminals that have replaced or soon will replace typewriters in the nowsroom. Some three-quarters of all major newspaper plants now use computers in some production process: companies using video-display terminals rose to 57 per cent from 37 per cent among American Newspaper Publishers Association members in just one year - 1975.

More than 90 per cent of ANPA members are using photocomposition machines for some or all of their type today and more than half of ANPA plants now use offset printing. At the more than 500 newspapers plants still using letterpress printing, instead of offset, more than half now use cold type composition compared with none in 1971.

The changes wrought at newspapers by these new devices have been profound and, as technologies are expanded, an even greater impact is expected. For example, some computer systems now are being developed by which editors can design full newspaper pages on a television screen. When perfected, that will permit elimination of the time-consuming process of pasting up cold type pages column-by-column and advertisement-by-advertisement.

Not only is the complex factory process being changed but also readers should be served with fewer printing errors and perhaps, a better-looking product.

Newspaper people like to call it the "daily miracle" - the transformation of ideas inside a writer's brian to printed columns of type in a folded edition of several sections, that appears each day at the reader's doorstep or newsstand.

Indeed, there is something miraculous about turning out hundreds of thousands of newspapers during just a few hours every day.

Editors at The Washington Post, for example, find it difficult to get their reporters to start writint major stories for the next day's issues until about 5 o'clock in the afternoon. But by 10:15 p.m., the presses are rolling with those stories - plus headlines, photographs, other graphics advertisements.

Despite all the romance about writing for newspapers - the "soul" of the journalism business - it is the manufacturing machines and workers who perform the miracle.

Several corporations today are competing to provide newspaper publishers with ever more modern machines to make the production process more efficient. Mergerthaler Linotype Co., Hendrix Electronics Inc., Raytheon Co. and Harris Corp. are among the firms that are selling computer-based systems that centralize several processes.

Although there are some differences in the various products and separate newspapers have followed their own timetables for implementation of the new technology, a general pattern for production has emerged that will be in use at most daily newspapers by the end of this decade.

To the general public, the most visible symbol of new technology will be climination of most typewriters from the nation's newsrooms.

Working away from the office or at a desk without a typewriter, the reporter will gather information for his or her report. When ready to compose a story, the reporter will sit down before a television terminal with an attached typewriter-like keyboard and type out the report; if away from the office the reporter may dictate by telephone to another person but the end result will be the same - someone has to type it into "the system."

This overall "system" will consist not only of dozens of terminals for use by writers and editors but also computers for storing all the material on file, which can be called up on various display screens at an instant for editing and rewriting.

News reports sent by such syndicates as the Associated Press also will be filed into the computer for use by the editorial staff. Similarly, advertising copy will be entered into the computers.

When editors and advertising executives are satisfied with the material, they "send" it electronically to photo-composition machines which, within a few moments, produce the stories or ad copy printed out on white sheets of paper. Composing room workers cut and paste these sheets onto empty pages, following a format (called a "layout") drawn by editors, adding headlines or photographs where directed.

When a page is completid, it is sent to a camera room where a photo is taken of the entire page. Subsequently, a plate is made of the page for the presses and attached for the press run.

As the presses roll, complete sections are printed and the machines automatically cut newsprint and fold the papers - spitting them out into stacks of complete editions or sections of a larger paper.

A Sunday newwpaper often includes several press runs - with some sections printed early and inserted with the remainin parts prior to delivery. Distributing trucks are loaded up with bound stacks of the papers and they are moved throughout an area to local delivery person sand newsstands.

This seems complex enough to accomplish in several hours each day. But the new technology climinates many cumbersome steps still in use at many large dailies.No longer needed, for example, are the separate machines to cast lines of type and headlines. In addition, newspaper editors and executives expect fewer printing errors because once a story is in the computer, that's it. There is no retyping of copy for production.

In effect, editors will gain a larger responsibility for the accuracy of what finally is printed. No longer will they be able to blame typographical errors on typesetters in the composing room.