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ISDN, which stands for Integrated Services Digital
Network, is a system of digital phone connections. This system allows
voice and data to be transmitted simultaneously across the world using
end-to-end digital connectivity.
With ISDN, voice and data are carried by bearer channels (B channels)
occupying a bandwidth of 64 kb/s (bits per second). Some switches limit B
channels to a capacity of 56 kb/s. A data channel (D channel) handles
signaling at 16 kb/s or 64 kb/s, depending on the service type. Note that,
in ISDN terminology, "k" means 1000 (103), not 1024 (210)
as in many computer applications (the designator "K" is sometimes
used to represent this value); therefore, a 64 kb/s channel carries data at
a rate of 64000 b/s. A new set of standard prefixes has recently been
created to handle this. Under this scheme, "k" (kilo-) means 1000 (103),
"M" (mega-) means 1000000 (106), and so on, and "Ki" (kibi-)
means 1024 (210), "Mi" (mebi-) means 1048576 (220),
and so on.
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