Appeal No. 1998-2672
Application No. 07/955,768
to one of ordinary skill in the art at
the time the invention was made to modify
the Averbuch system by providing the
teaching of the Ernst backup clock system
in order to maintain a faultless synchronization
of a backup clock to a reference clock as
taught by Ernst (Col. 2, lines 3-5). [Answer,
pages 3 and 4.]
After reviewing the Averbuch and Ernst references, in
light of the arguments of record, we are in agreement with
Appellant that proper motivation has not been set forth for
the Examiner’s proposed combination so as to establish a prima
facie case of obviousness. In making this determination, our
interpretation of the disclosure of Ernst coincides with that
of Appellant. Rather than suggesting the improvement of the
stability of a backup clocking source by utilizing a primary
clocking source signal as in the appealed claims, the problem
addressed by Ernst is the elimination of glitches such as
phase shifts on switching from active to backup central clock
generators. Ernst attacks this problem by providing a
technique for synchronizing the generated clock signal within
each of the active and backup central clock generator circuits
with an external reference signal during certain window
periods tied to the generated clock signal (Ernst, Figs. 2 and
7
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