ISDN Digital Subscriber Line (IDSL) transmits data digitally (rather than analog) on a regular twisted pair copper telephone line, across existing ISDN lines, at a rate of 144 kbit/s, slightly higher than a bonded dual channel ISDN connection at 128kbit/s. The digital transmission bypasses the telephone companies central office equipment that handles analog signals. IDSL uses the ISDN grade loop without Basic Rate Interface in ISDN transimission mode. The benefits of IDSL over ISDN are that IDSL provides always-on connections and transmits data via a data network rather than the Carriers voice network.

IDSL also avoids per-call fees by being generally billed at a flat-rate.

IDSL is not available in all countries.

ISDN Digital Subscriber Line | IDSL | IDSL | Digital Subscriber Line | Integrated Services Digital Network