Appeal No. 2001-2270
Application 09/235,529
chip shown in Fig. 9 (RBr8). It is argued that the examiner has
not cited a reference in which any dialing signals that are
attenuated by more than 30 dB are detected by any type of
detection device (RBr9).
While the power to the central office may be attenuated by
30 dB, as shown in appellants' sketch at RBr6, it does not appear
that the voltage across the parallel attenuator is changed.
Therefore, appellants have not shown that a special voltage
detector is required or that one of ordinary skill in the art
would not know how to detect the DTMF signals without undue
experimentation. Moreover, it does not appear from appellants'
disclosure that the invention is the circuitry for detecting an
attenuated signal. No special detection circuitry is claimed.
Appellants argue that the references cannot be readily
combined without the inventive modifications as recognized by the
applicants, nor is there any indication in the reference that
they should be combined (RBr8).
"[T]he test [for obviousness] is what the combined teachings
of the references would have suggested to those of ordinary skill
in the art." In re Keller, 642 F.2d 413, 425, 208 USPQ 871, 881
(CCPA 1981). While Eaton does not expressly say that a parallel
attenuator should attenuate by 30 dB, one of ordinary skill in
the art would readily appreciate that the 30 dB attenuation
between the telephone and central office for a serial device in
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