What is ISDN?

ISDN is an abbreviation for the English "Integrated Services Digital Network", or "Integrated Services Digital Network".

Integrated Services Digital Network evolved from a telephone integrated digital network to provide End-to-end digital connectivity to support a wide range of businesses, including voice and voice services, to provide users with a standard set of multipurpose user-network interfaces. In short, it is a network, namely a set of transmission equipment and a set of switching equipment to provide a variety of telecommunications services transmission and exchange, to improve the efficiency of the network and to provide users with greater convenience. The fundamental point of implementing this network is to provide End-to-end digital connectivity.

ISDN (Integrated Services Digital Network) is a traditional telephone service replacement product, uses the telephone line as the data transmission carrier, it may transmit the voice and the data simultaneously on a telephone line.
At present the telephone service provides two kinds of rate ISDN services, Basic rate ISDN (BRI) and base Group rate ISDN (PRI). For families and small and medium-sized users, BRI is the most suitable and most commonly used, the PRI provides faster data transmission capabilities, so it is suitable for large users.

Basic Rate ISDN (BRI)

A BRI consists of two channels, two B Channel to transmit data, each channel transmission rate is 64K, used to transmit data (two channels bundled together to provide 128kb/s transmission rate), a D Channel, is the control channel, the rate is 16K, used to transmit control signals.

Base Group Rate ISDN (PRI)
The base group Rate ISDN (PRI) is much faster than the BRI, consisting of 23 64K B channel and a 64K D channel, with a total rate of 1536kb/s, whereas in Europe the PRI is made up of 30 64K B-Channel and a 64K D Channel composition, the total rate is 1984kb/s.

Compared with the traditional modem, although the modem's transport protocol is the standard 56K, but this is only a theoretical rate, in the actual use, generally can only achieve 50k,45k or lower connection rate, while uploading files, Speed will not exceed 33.6K, at the same time, the transmission rate of modem and line quality has a certain relationship, if the line quality is not good, will also affect the transmission rate.

ISDN is not susceptible to interference because it transmits data signals. At the same time, if you use only one channel to surf the Internet, another channel can call at the same time without any impact on the Internet.