Definition: "Isdn" is short for Integrated Service Data Network, which connects to fixed-line networks via a digital interface (dial-up). It provides voice, data, and video services over IP with speeds up to 1 Gbps. Detailed definition: - Isdn stands for Integrated Service Data Network, which includes both voice and data services. - It uses dial-up technology and has up to 1Gbps speeds. - It is designed to connect fixed-line networks to the internet via a digital interface (dial-up).