THIRD AREA CODE SET TO DEBUT FOR TOLL-FREE NUMBERS.

Byline: Gregory J. Wilcox Daily News Staff Writer

A new toll-free area code, 877, debuts at 10 a.m. Sunday courtesy of the technology revolution.

And we were just warming up to that other new toll-free prefix, 888, implemented in March 1996 to spell relief for the old standby, 800.

Unlike cyberspace, or outer space for that matter, the world of area codes has a finite boundary.

Each code can spin off 8 million telephone numbers, which was enough for the old 800 to last for 20 years as the only toll-free prefix. But these days, with the soaring population of modems, pagers and cell phones, to say nothing of businesses looking for an edge, 8 million is not a big number.

The 888 prefix came along just about the time everyone jumped on the information superhighway and the business world started tripping over itself trying to entice consumers to make a free phone call in hopes of making a sale. In the last two years the telecommunications industry chewed through the supply of available numbers at a ferocious pace.

By last fall, the pool of available toll-free numbers was disappearing at a clip of about 400,000 a month. That's not surprising, considering that 34 billion toll-free calls are made each year and 200 telecommunications companies can dole out the tightly rationed allotment of the numbers.

The Alliance for Telecommunications Industry Solutions, a group composed of federal regulators and telephone company officials, administers the toll-free phone number program. Toll-free prefixes 866 and 855 are waiting in the wings.

There are currently about 14 million toll-free numbers in use nationwide, so we're into some serious number-crunching here. Telecommunications industry analyst Jeffrey Kagan, owner of Kagan Telecom Associates in Atlanta, said toll-free numbers are being snapped up quicker than anyone ever imagined.

``Now you can use them for pagers and businesses use them for everything,'' he said. ``It used to be that an 800 number was a competitive advantage but now they are so cheap that just about every business uses them as a way to do business.''

One reason is that starting in 1993, toll-free numbers became portable, meaning customers could take them along when they changed phone carriers or moved.

Then along came vanity numbers like (800) CAR-RENT (National Car Rental's reservation number). When the 888 prefix was introduced, vanity numbers immediately gobbled up 380,000 possible combinations.

This time, to make the pool last a little longer, vanity numbers with the 877 prefix will be passed out on a first-come, first-served basis, rather than giving current holders the right of first refusal.

Telephone companies like MCI have spent the past several months getting ready for the new number, updating computer billing systems so 877 calls are recognized as toll-free, reprogramming switching offices so the equipment recognizes the new code and implementing advertising campaigns so consumers know that dialing 877 is free.

``That stuff doesn't happen overnight. It takes a while to get the software upgraded and run tests,'' said Paul Adams, an MCI spokesman.