What is a videodisc player that Ray Kuehne, a 35-year-old computer technician from Atlanta, Ga., should be standing outside an appliance store at 5:30 in the morning so he can be one of the first to shell out 695 smackers and buy one?

A videodisc player is a machine that plays videodiscs, that's what a videodisc player is. A videodisc looks like a shiny, silvery 12-inch LP record, but the difference is, when you hook the player up to a TV set and plop in a disc, it plays back pictures as well as sound-old movies, not-so-old movies, documentaries, instructional films and what-have-you. What you probably don't have is a videodisc player, because only now, after years of delay, are the machines being test-marketed, and only, at the moment, in Atlanta.

Because the videodisc player uses a laser beam to turn its electronic pizza pie into TV-the way a record player uses a needle, basically-the gizmo has a futuristic aura about it. In fact, the technology has been around for years. It's the marketing strategy that's being worked out. Does America have space in its living room and its budget for a new luxury toy only one year after the introduction of the video cassette recorder?

The essential functional difference between the video cassette recorder, or VCR, and the videodisc system is that with VCRs, you can record as well as play back material; with videodiscs, you cannot record anything. You can only buy discs of pre-recorded material and play them back. One reason the huge MCA-Universal company may have so long delayed introduction of its version of the players is that it has joined with Walt Disney Productions to sue the manufacturers of VCRs on copyright infringement grounds. This is still in the courts and MCA may be waiting for a decision before it tries selling its machine.

VCRs and videodisc players will be competing for essentially the same market. There is a school of thought in the consumer electronics industry which holds that the public will go for the disc - even though they can't record on them-because they'll be easier to use and cheaper to buy.

The machines being test-marketed in Atlanta are made by Phillips Electronics for the Magnavox company and are called Magnavision. But other companies, in addition to MCA, are gearing up for the entrance of the disc. RCA is tinkering with a Selectavision videodisc system of its own, and the Victor Co, of Japan, known as JVC in the U.S., has unveiled its own "VHD/AHD" - which stands for "Video-Audio High Density Disc System" - but only in Japan so far.

Just when these devices will be available on a large scale to American consumers is a matter of much speculation and no certainty.

Ray Kuehne was one of the first consumers and he was lucky. Two of the three outlets selling the devices and Discovision records, which provide the images and sounds, sold out of their limited supply that morning. The manager of one shop reported that a Japanese electronics firm had dispatched an emissary here who was offering purchasers up to $3,000. Six days after his purchase, Kuehne turned down $2,000 for it.

Nestled on a console color television set in Kuehne's living room, the videodisc player resembled a squat, metal icon. A Salvador Dali lithograph hung above it. Lush plants and pieces of bright orange Danish contemporary furniture surrounded the video display. Kuehne's wife, a microbiologist, sat quietly on a sofa nursing a whiskey and soda. His two young sons sprawled on the carpet watching their father load one of the plastic and metal Discovision records on to the player. Because of the disc's intricate configurations (each half-hour side contains 456,000 images), light sometimes bounces off the shiny orbs, producing a rainbow of colors. Kuehne's boys were entranced by the chromatic dazzle.

Kuehne was excited. His voice was at a fever pitch. "This is borderline magic I have here. It really is." Kuehne could not let the thought go. "This device increases my sense of awe and wonder about the world." Then he predicted, "It's going to alter the very way we live."

Kuehne is an intense, articulate man who possesses a lifelong passion for electronics and elaborate sound systems. The basement of his modern, north Atlanta home is cluttered with expensive amplifiers, receivers, woofers and tweeter. "I don't even think Phillips Electronics or Magnavox knows how incredible this thing is." Kuehne pressed a switch on his machine, turned away from it and smiled.

The player emitted a whirring hum-its motor was revving the disc up to a speed of 1,800 revolutions perminute. A series of orange and white kaleidoscopic images flickered across the television screen. (The machine is attached to the antenna jacks of most color television sets. No needle ever touches the playing surface; the videodisc player's laser beam picks up the images and sounds from the record, turns them into a television signal and transmits the signal back into the television set.) Two Advent speakers hidden in the room's corners carried the sound.

Finally, a snow-covered castle flashed onto the screen. A motive version of Cinderella, "The Slipper and the Rose," starring Richard Chamberlin, came on, Kuehne's sons - even though this was their fourth time to see the movie in six days - abandoned their $6-million Steve Austin doll and watched intently.

Magnavox's mid-December introduction of its videodisc player to the Atlanta market marked the end of months of speculation in the television industry. For the past five years, electronic journals had been announcing that a videodisc system that worked basically on the principles of the phonographic turntable was soon to be merchandised for the public. But an article in a November TV Guide announced that Magnavox would be test-marketing the machines in Atlanta. The story initiated a two-week search by Kuehne.

First, he called Phillips' offices here-they demurred. Then he called Magnavox's offices here-and they referred him to a public relations branch in Indiana. The indiana people told him that the TV Guide story was a false leak and that Magnavox could offer him no factual information about the videodisc system.

Frustrated, Kuehne decded "to go harass some salesmen in Magnavox outlets here because they had a financial stake in it all," He learned that a shop in a mall 30 miles from his home would have five machines on the date that sales began in Atlanta. The store opened at 10. He figured the people who really wanted the device would arrive at 8. "So I decided i'd get there at 5:30, and sure enough by 8 five people were already in line and this one guy then showed up with his lawn chair ready to wait, saw us standing there, folded the thing back up and went home."

MCA offers a videodisc library composed of 200 different records. Selling at $15.95 apiece are videodisc of Fellini's "Casanova," "Animal House," "Slaughterhouse Five" or Walt Disney's "The Prince and the Pauper." Prices are lower for older movies or educational films. "To Kill a Mocking bird," with Gregory Peck or the original "Dracula" starring Bela Lugosi are $9.95. For $5.95, there are such titles as "V.D.: The Hidden Epidemic" or "Total Fitness in 30 minutes a Week."

Kuehne purchased only eight discs when he bouth his machine-a caution that now disappoints him. "They're all sold out now," he complained.

It was getting late and the children were now bored by Cinderella. "We want to do the number ones," the 5 year-old said.

"Okay," Kuehne acquiesced, setting down a beer in order to fetch another disc. This one, called "Math That Counts," contained animated vignettes nica. Each episode imparted a bit of numbers. "It's sort of a souped-up 'Electric Company,'" said Kuehne as his children watched an episode about addition. In 15 minutes, the boys were squabbling and crying again.

"All right now, off to bed," Kuehne's wife ordered. Reluctantly the two boys marched out of the room. Meanwhile, Kuehne pulled out a disc of Zubin Mehta conducting the Los Angeles Philharmonic Orchestra playing "Bolero." More drinks were mixed. As the repetitive strains of the symphony boomed up toward the room's ceiling and an imaginatively edited film of the orchestra flitted across the screen, Kuehne raved on about the machine.

"Don't you see what this thing is going to do? Why, with 56,000 images on each side of a disc, you could have every important piece of art in galleries all over the world on just one of plastic and have it for your own. Think of the books you could read on your screen," Kuehne exuded, running a hand back through a shock of long, curly blond hair. "With the cost of paper going up and all, it would be a great bargain. You can get hundreds of thousands of words on just one disc.

"Why for the same price as phonograph record, you can not only buy the sound, but also the images and if you want to go get a beer all you've got to do is flick the switch," he said as he walked to the player and did just that. "Let's get a drink," he urged, walking into his kitchen. It was almost midnight, and as he left the room, the image of Zubin Mehta, his face contorted in an urge to the orchestra, lingered on the screen, glowing, waiting for touch of Kuehne's finger to continue the performance.