IDSL is a system in which digital data is transmitted at 128 Kbps on a regular copper telephone line (twisted pair) from a user to a destination using digital (rather than analog or voice) transmission, bypassing the telephone company's central office equipment that handles analog signals. IDSL uses the Integrated Services Digital Network (Integrated Services Digital Network) Basic Rate Interface in ISDN transmission code.
IDSL is a technology developed by Ascend Communications (now part of Lucent Technologies). IDSL is only one possible technology in the Digital Subscriber Line approach (of which Asymmetric Digital Subscriber Line or Asymmetric Digital Subscriber Line is best known) and an expedient approach that allows use of existing ISDN card technology for data-only use.
The differences between IDSL and ISDN are:
- ISDN passes through the phone company's central office voice network; IDSL bypasses it by plugging into a special router at the phone company end
- ISDN requires call setup; IDSL is a dedicated service
- ISDN may involve per-call fees; IDSL may be billed at a flat rate with no usage charges