Appeal No. 2001-2270
Application 09/235,529
a claim are disclosed in the prior art, it is not inventive to
discover the optimum or workable ranges by routine
experimentation.").
Appellants argue that neither reference discloses a method
of detecting such attenuated dialing signals while inhibiting
their transmission so that they are not detected at a central
office (RBr9; RBr10).
We agree with the examiner that one of ordinary skill in the
art that the limitation of "at least 38 dB" would have been
determinable by routine investigation in view of the guidance
provided by Stevens and, hence, obvious. Stevens informs one
skilled in the art that the attenuation should be sufficient "so
that the amplitude of the signals on the telephone line is below
a threshold of the central office, so that the central office
does not recognize the signals as representing a telephone number
entered by the user" (col. 2, lines 42-45). Thus, attenuation is
taught to be a result effective variable for preventing detection
of tones by the central office. Appellants note that the "AT&T
central office switches typically reject DTMF tones less than
-38.2 dBm per tone" (spec. at 9, lines 17-18). One of ordinary
skill in the art, seeking to determine the level of attenuation
which would prevent detection by the central office would have
been able to determine this information with routine
investigation. We conclude that the examiner has established a
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