Currently, even the fastest modems commonly available often make browsing the Net a frustratingly slow experience.

I had one of the fastest telephone-based modems you can buy in my home office, with a theoretical top speed of 56 kbps.

Today's fastest standard modems are rated at 56,000 bits a second but are actually limited to 52,000 bits a second.

Today's fastest modems cost about $150, while access to the Internet typically costs $20 a month.

But just as the very fastest modems can still command premium prices, so can very small ones.

But the breakthrough that led to today's fastest modems was the idea of sending several tones at the same time, creating a mini-symphony of sounds in each symbol.

With traditional phone lines, even using the fastest modems now available, many customers find that surfing the Net is as exciting as watching paint dry.

The fastest conventional modems available today, at 56K, can download nearly 56,000 bits per second.

And the National Science Foundation is contributing $15,000 a year for a high-speed data line that sends and receives electronic information four times faster than the fastest modems.

I.S.D.N. transforms all information into the ones and zeroes of computer code and speeds up data transmission by nearly 15-fold over today's fastest modems.