In a laboratory several stories above the New York Stock Exchange trading floor, experimenters putter with hand-held computer terminals, fingertip- and voice-activated computers and videodiscs.

At the American Stock Exchange, technicians are crawling under the floorboards installing the guts of a wireless telephone system and planners are grappling with the problem of how to provide 600 walkie-talkies, all operating at different frequencies, without drowning out radios and televisions in the area.

In an industry not known for rapidly changing operations -- and where major physical overhauls are as easy as rebuilding a zoo with the animals still in residence -- modernization is proceeding inexorably anyway.

The NYSE opened its product-analysis laboratory last fall to provide a place to experiment with new technology that might be applied to the exchange. There, brokers can play with the gadgets in an experimental setting and register complaints and praise.

A few blocks away, the Amex is testing its own, more limited array of electronic marvels.

"We build working models," said Erik J. Steiner, who directs the laboratory at the NYSE. "If you can get a user to sit down and work with it as if his livelihood depended on it, you get a more usable reaction," he said. "That's what we're in the business of."

Among the models that Steiner and consultant Michael S. Lightman of the Securities Industry Automation Corp. are working on is a hand-held terminal for use by NYSE reporters. Reporters work for the exchange, sending information on transactions to ticker tapes and other, more modern receivers and to the rapidly moving illuminated scoreboard that dominates the trading floor.

Now they hover on the edges of the action at the trading posts, listening to trades and marking special sensitized cards with a pencil to record the figures that reflect the market's movement. The cards are fed into a machine that automatically sends the information to the scoreboard glowing green above the heads of the traders. Depending on how many reports are queued up on the computer, that system can be slower than the old system in which the figures on the scoreboard were manually changed, according to traders.

The terminals, which will be tested on the floor this summer, are tailored to the task at hand. Each button on a panel of 15 buttons is the symbol for a stock, part of a keyboard that allows reporters to report trades rapidly. The terminals also can give a history of the stocks' activities. Besides being used by reporters, the terminals might also be used by brokers to report to their offices on transactions, using five to seven keystrokes.

Touch-sensitive screens, which produce the information indicated when the user touches one of a list of alternatives offered on the screen, and voice-activated terminals trained like a well-mannered dog to respond to the tone of an individual's voice also are being tested.

The voice-activated computer can be trained to respond to 24 different utterances (words or phrases that don't exceed two seconds) by repeating the commands 10 times each. For instance, by repeating "who's-the-fairest-of-them-all" 10 times you could train the computer to respond "you are," or by repeating Xcorp 10 times you could train the computer to produce the latest prices for X company's stock.

"We're trying to see if there are places on the floor where it enhances what the people there are doing," Steiner said.

The laboratory has videodiscs similar to iridescent disks being used to bring movies to homes. In the case of the NYSE, the discs are used for training people who work at the exchange in the use of new systems."We have 2,800 people on the floor, and we're training people in new procedures which are coming along fairly rapidly now," Steiner said.

The exchange is experimenting with intelligent credit cards, regular-sized plastic cards with 4,000 characters that might allow transactions to be recorded and appropriate debits made.

Experiments at the Amex are less exotic. "The thrust of most is to determine the most efficient manner of communicating between brokers and their clerical help," said Kenneth Leibler, senior vice president for administration and finance.

At the Amex, brokers communicate with brokerage-firm employes confined to booths off the floor by using an elaborate system of hand signals developed early in the century when the exchange was literally in the street and a firm's employes hung out windows to shout instructions to buy or sell.

The Amex has no plans to modernize the hand signals -- which with the noise and the rapid tracks brokers make around the floor give the exchange something of a riotous hog-auction atmosphere -- out of existence. But planners are working on ways to improve communications when something more complicated than sending orders or reporting transactions is involved.

Brokerage-firm employes can beep traders on the floor. Soon they may be able to get them directly on radio telephones, the support equipment for which is being installed under some parts of the trading floor. In those squares, painted brown, brokers can pick up a wireless phone. "We're still in the process of testing," Leibler said.

A walkie-talkie system is being designed that would allow the broker to be completely mobile rather than confined to certain floor areas.

Making such changes is "a very difficult process because all the work has to be done while we're operating, which means most of the work is done on weekends and nights," Leibler said. "Everything is done on premium time and has to be carefully thought out to avoid any interference with the operations." h

"We're leaving no stone unturned in hands-on experiments," Steiner said at the NYSE. "On the whole, the bulk of the membership is becoming accustomed to change. They've gotten used to the idea that there's nothing wrong with change."