Integrated Services Digital Network (ISDN) is a telecommunication technology for sending voice, video, and data over traditional telephone lines or digital telephone wires. It enables broad bandwidth digital transmission over public telephone networks. This means more data can be sent at one time. ISDN can support data transfer rates for up to 64-128 Kbps (kilobits per second).
When ISDN was first introduced as a viable access technology, it brought a lot of promises with more features and capacity than dial-up. ISDN initially achieved only a small market share in the Internet access market. Nevertheless, there was no doubt that it paved the way for more popular Digital Subscriber Line (DSL) and cable-based last-mile technology.
ISDN connectivity consists of a system that uses telephone wires. However, it is a very sophisticated digital technology. The technology behind it is circuit switching. It implies that it uses a dedicated line to transfer data and phone conversations. Before transmission, voice is also converted to digital data. The ISDN modulation can send data at a much faster rate digitally over traditional telephone cables. Experiments and experience have shown that ISDN is both faster and has a much higher quality than dial-up Internet access.
ISDN is categorised based on number of channels. The first version is called Basic Rate Interface (BRI). It consists of two channels, operating at 64Kbps. The second type is called the Primary Rate Interface (PRI). This increases the capacity to 1,544 Kbps by using 23 bearer channels. ISDN can be used for video conferencing, security monitoring, LAN interconnection, and high-quality audio.
It doesn’t however, offer enough bandwidth to stream high-quality video.