ISDN (Integrated Services Digital Network)

Definition: Integrated Services Digital Network is an international standard for switched, digital dial-up telephone service for voice and data.

What This Means: Analog telephones and fax machines that are used over ISDN lines have their signals converted into digital by the ISDN terminal adapter. ISDN enjoyed a surge of growth in the early days of the Internet because it provided the only higher speed alternative to analog modems in many areas. Still working in many behind-the-scenes applications, ISDN is rarely used for Internet access.

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