Appeal No. 1998-2874
Application No. 08/568,718
Claim 1 is illustrative of the claimed invention, and it
reads as follows:
1. A noise cancellation circuit for use with a digital
signal, comprising:
a plurality of equally weighted cells for receiving
the digital signal and for providing an analogue
output signal in dependence upon the value of the
received digital signal; and switching means
for dynamically switching a number of the
plurality
of cells according to a sequencing scheme, wherein
the sequencing scheme comprises a first sequence
arranged to switch each of the plurality of cells
in a sequential order an equal number of times, and
a second sequence arranged to randomly define, using
a random number generator, one of the plurality of
cells as a starting position for the first sequence,
such that low frequency tone generation within the
analogue output signal is substantially
eliminated.
The references relied on by the examiner are:
van de Plassche 3,982,172 Sep. 21,
1976
van de Plassche 4,125,803 Nov. 14,
1978
Jackson 5,221,926 Jun. 22,
1993
Claims 1 through 10 and 12 stand rejected under 35 U.S.C.
§ 103 as being unpatentable over the admitted prior art or
either of the van de Plassche patents in view of Jackson.
Reference is made to the brief and the answer for the
2
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