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In addition to choices between the actual logic, engineers
designing the encoded programs for the control mechanisms of a
modern digital switch also had the option to place various parts
of the encoded logic in software (i.e., the encoded medium that
will be loaded into the central processing unit) or firmware
(permanently encoded chips located in the central processing unit
or in microprocessors located throughout the switch). The
choices made were determined to a large extent by the switch's
architecture. A switch manufacturer writes the programs and
decides how they would be incorporated into the processors in the
context of the design requirements of a particular model. Just
as the architecture of the switch affects the programming, the
programming limitations and requirements affect the architecture
of the switch. The programming is also affected by the given
location. Due to the unique parameters of a given location,
programs are invariably location specific.
Because of the interrelationship of the architecture and
programming and the unwillingness of manufacturers to sell the
switch hardware without the switch software, programming for a
digital switch is written by the manufacturer of the switch and
is not available from third parties. Absent the manufacturer's
programming, the manufacturer's hardware cannot operate. Because
the design of the programming is specific to the architecture and
even the location of the digital switch, not only can the
programming of one manufacturer not be used on the equipment of
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Last modified: May 25, 2011