The telephone system of the future. ISDN is a technology which permits transmission of data on telephone lines at an extremely high speed, roughly 27 times faster than traditional technology. It uses digital signals instead of analog, and is therefore very popular among users who use telephone lines to connect computers to each other. Because of the digital signals, greatly improved audio quality is possible over phone lines. Availability of this service is dependent on your local phone company. Unfortunately by the mid 1990’s many geographical areas still did not have ISDN, or it was prohibitively expensive. About the only drawback to ISDN is that it will require new telephones to take advantage of it.