What Is ISDN?

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into an analog format to travel through the public phone network.
However, there is a limit to the amount of information that a common analog
telephone line can hold. Currently, it is about 28.8 kbit/s. [Hopkins] ISDN
allows multiple digital channels to be operated simultaneously through the same
regular phone jack in a home or office. The change comes about when the
telephone company's switches are upgraded to handle digital calls. Therefore,
the same wiring can be used, but a different signal is transmitted across the
line. [Hopkins] Previously, it was necessary to have a phone line for each
device you wished to use simultaneously. For example, one line each for the
phone, fax, computer, and live video conference. Transferring a file to someone
while talking on the phone, and seeing their live picture on a video screen
would require several expensive phone lines. [Griffiths] Using multiplexing (a
method of combining separate data signals together on one channel such ...

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are provided for user information at higher
bit rates. [Stallings] There are two types of ISDN service: Basic Rate ISDN
(BRI) and Primary Rate ISDN (PRI).

BRI: consists of two 64 kbit/s B channels and one 16 kbit/s D channel for a
total of 144 kbit/s. The basic service is intended to meet the needs of most
individual users. PRI: intended for users with greater capacity requirements.
Typically the channel structure is 23 B channels plus one 64 kbit/s D channel
for a total of 1.544 Mbit/s. H channels can also be implemented: H0=384 kbit/s,
H11=1536 kbit/s, H12=1920 kbit/s. [Stallings]

In this paper, I will concentrate on defining the specifics of Basic Rate ISDN
for local loop ...

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