Appeal No. 96-3366
Application 08/292,700
An audible indication of coverage area limits allows a user to initiate corrective action, if necessary.
This is distinct from prior art digital communication systems which, due to the reduction of recovered
noise brought about by error correction techniques, do not allow a user to judge their proximity to
coverage area limits through the recovered noise.
The Prior Art
In Figure 1, Marui illustrates apparatus for use in a cellular mobile telephone system comprising
means for alarming (17, 18) at least a user operating the apparatus in response to a drop in signal
strength of radio frequency signals received over an established communication channel (13, 11, 22,
23) when the apparatus approaches a boundary of service area in a cellular mobile telephone system.
The signal strength is repetitively checked to determine if it has fallen below a first predetermined signal
strength value. When the signal strength falls to or below a second predetermined signal strength value,
the radio telephone apparatus causes a disconnection of the telephone link and returns the apparatus to
a standby mode.
The Rejection under 35 U.S.C. §103
Appellants argue that Marui does not teach or suggest the use of an analog RF channel in a
communication unit for generating an indication which is a controlled simulated analog RF channel noise
signal. It is asserted that an indication which simulates a phenomenon known to occur at coverage area
boundaries (i.e., recovered noise) is not obvious in view of Marui because the reference teaches
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