With the possible exception of "Buy low; sell high," Telemet America Inc. of Alexandria and Dataspeed Inc. of San Mateo, Calif., offer thousands of quotes that no one will ever find in Bartlett's.

The two companies -- now competing in the Washington market -- are selling a portable and up-to-the-minute way to keep track of the price of stocks.

They offer investors stock quotes using what amounts to a wireless ticker tape that fits snugly into a jacket pocket. At the office, over lunch or in a cab, just tap a few keys and the pocket calculator-like screen will instantly display prices of stocks from AAR to Zirvin.

Instant stock quotes don't come cheap. The pocket ticker tape costs $350 to $400, plus service charges of $20 to $50 a month.

"It's a nice business to be in," says Telemet Chairman Frederick Parsons. "We think we're the next generation of broadcaster."

With roughly 10,000 subscribers and 14 stations nationwide, Telemet's Pocket Quote service is both the largest and most prosperous of the wireless tickers. Parsons asserts that Telemet is "close to eight figures" in revenue and enjoys pretax profit margins approaching 40 percent.

Dataspeed's Quotrek portable stock quote service, on the other hand, currently has only 2,500 customers but "is coming on very strong," says Dataspeed Chairman David Lockton.

Quotrek just entered Washington last week and is now in 12 markets.

"I really don't think Dataspeed is really going to be around in a while," asserts Parsons. But Lockton is sanguine. He says there are some joint ventures in the works that will make Dataspeed the premier data broadcaster in the country.

"It's all going to come down to marketing," says one telecommunications consultant. "The services are basically the same. How you sell and how much you sell it for is going to make the difference."

The technological key to these services is tucked into FM radio broadcasts. They use a part of the FM frequency spectrum, which is not picked up by ordinary radios, called the FM subcarrier. These subcarriers don't carry rock and roll or classical music. Instead, they allow broadcasters to pipe out digitized bits of information that can be picked up by special receivers. It's sort of a radio for data.

The subcarrier transmitter pumps out a continuous stream of stock quotes. Equipped with a computer chip, special pocket-size radio/decoders can be programmed to capture and store the desired quotes for the investor's portfolio. The subcarrier also can transmit other types of information, including foreign exchange rates, commodity prices and news briefs. Before the stock quote services came along, FM subcarriers most often were used by Muzak services to transmit background music.

Market analysis revealed that investors who wanted to know in an instant just how their portfolios were doing would be willing to pay a premium for the service.

Parsons estimates that there are 400,000 potential customers in the Washington area alone. He says Telemet and Dataspeed are competing for between 3 percent and 6 percent of that number.

Although many stock quote services already exist, they require a physical link to Wall Street's computers.

By going over the airwaves, Pocket Quote and Quotrek let their subscribers get the data they want no matter where they are. The devices can be programmed to beep when prices of chosen stocks begin to move or hot financial news flashes over the wires.

"When Bankers Trust lowered the prime," says Telemet's Parsons, "our subscribers knew about it in 10 minutes through UPI. The unit beeped, and a message flashed across the screen."

Telemet's Pocket Quote, which has been on the market for slightly more than two years, offers options prices and commodity futures contract quotes as well as stock quotes. The receiver is priced at $349, and a monthly subscription fee is $20. That compares with Quotrek's $399.95 price per unit and $50 a month fee.

Dataspeed's Quotrek does not yet carry options or commodities. Lockton says those arrangements will be completed shortly. He also points out that Quotrek offers "real time" stock quotes while Pocket Quote's are delayed 15 minutes.

But the services are more similar than they are different. Consequently, several observers believe there will either be a price war between the services or they will do everything they can to offer special features to differentiate themselves from the competition.

Lockton speculates that there may be tie-ins between his digital network and television game and sports shows. Both he and Parsons talk about using subcarriers to distribute data and software to personal computers.

For now, though, both companies are counting on capturing the customers who want to be able to reach into their pockets to find out how fast the bulls and bears are running.