Basically though, it is good to keep in mind that DSL means copper wires with a computer digital network. Whereas ISDN means the telephone switched digital network is used.
Speed varies according to distance and wire gauge.
Right now DSL service cannot reach beyond 18,000 to 22,000 feet from the telephone central office. As far as I know, DSL is becoming available in Merrimack Country Telephone Company territory. ISDN is available. This would mean 128kbps service with both telephone and data on the same line as dial-up, however. Today's analog modems routinely offer 28.8kbps or 33.6kbps and, in most instances, 56kbps.