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Travis Russell

"The IP Multimedia Subsystem (IMS): Session Control and Other Network Operations"

These relays made up an intricate maze of circuits and connections,
all based on the dialed digits.
The digits themselves began taking on meaning. Communities were once referred to
as ???exchanges???, serviced by a switch. The switch was identified by the first set of digits
dialed. Once the switch was reached, the remaining digits identified the subscriber to
be reached within that switch.
This allowed telephone companies to interconnect hundreds of switches to one another,
automating the entire connection process. Operators were no longer needed, and
subscribers could dial any place they wanted (although in the beginning they could
only make local calls).
As the technology evolved and switches became digital, there was much more that
could be done with telephone numbers. The numbers were extended in length to support
long-distance and international dialing, further removing the human factor from
the telephone experience.
Believe it or not, telephone numbers have long been viewed as unfriendly and difficult
to remember. Consumers have grown so accustomed to this form of identity, however,
that they soon began to memorize the exchanges by the telephone numbers.
For example, consumers know that the 212 area code is New York City. When a call is
received bearing the caller ID of 212, the call recipient knows that the caller is in New
York.


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