Appeal No. 2003-1663
Application 09/975,934
a logical "true" (conventionally represented as "1"), the output
is a logical "true" ("1"), and when one or more inputs are a
logical "false" (conventionally represented as "0"), the output
is a logical "false" ("0"). An "AND" operation is, by
definition, a "logical" operation, so "AND logical" to describe a
circuit is redundant. An "AND" operation is also, by definition,
a function, so "AND functional" to describe a circuit is
redundant. The terms "AND circuit," "AND logical circuit," "AND
functional circuit," and "AND logical functional circuit" all
have the same meaning. An "AND" operation necessarily implies
operation with digital signals, i.e., signals that represent
either a "1" or a "0." An analog circuit which performs an AND
function has to be operating using digital logic signals, i.e.,
with signals that the circuit interprets as "1" or "0"; it does
not make sense to define an "AND" operation in terms of analog
(continuous) signals. The statement in Digital Integrated
Electronics that "[i]n logical gates all inputs and outputs are
digital signals," only refers to the digital data representation
and does not imply anything about the implementation of the logic
circuits. Appellants may be confusing digital signals with the
circuitry that implements the signals. While there are some
logic implementations that could be considered pure digital
(e.g., a switch which is either closed or open), there are many
logic implementations that use analog devices to produce signals
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