Integrated Services Digital Network (ISDN) and Digital Subscriber Line (DSL) are types of networks in which the currant POTS lines permitting the data transmission with much higher speeds. The connected place should not be far from the nearest point of presence (POP) of the telephone company containing the special communication equipment. For ISDN this distance should not exceed 5.5 km. Moreover, for DSL the distance depends on technology and speed of transfer (the farther the less speed). These technologies refer to as technologies of last mile, as they are developed for delivery of the data from the user up to POP.
Ideas of transition POTS for digital data processing, in which the end subscriber transfers the data only in the digital form expressed for a long time. Originally, it was planned that ISDN would completely replace existing digital POTS. But as a result of long process of creation and change of the standards, and also because of high technical complexity of the user interface ISDN stay as alternative to dial-up. The greatest distribution ISDN has received in Germany and France. In USA until recently, it was unpopular, due to the reputation as complex, difficult for installation and not reliable technology. The improvement of a situation with ISDN in USA began from 1994-1995, when ISP offered to their clients ISDN services for browsing in the Internet.
Approximately, in the same time the main manufacturers begun actively to produce network ISDN equipment and routers with ISDN support.
The constant tariff, and also installation and monthly payment are in most cases paid. As the tariff constant, then an opportunity perfectly approaches to use dial on demand for economy.
The ISDN connection approaches for those to whom connection is necessary for small intervals of time, for example for reading e-mails.
The connection is established almost instantly, as all connections are digital and there is no analog transformation.
There are two rate interfaces: BRI and PRI.
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