Appeal No. 2003-2072
Application No. 09/735,439
In operation, when switch 17 is closed and switch 16 is
open, output of routing switch 11 at node 18 is biased at a
negative potential and common-based transistor 13 in port
terminal switch 19 is in a conducting state. The input signal
hence, is routed to port 1. In this configuration, divider 25
has switch 26 closed and switch 27 open. Hence, the signal is
blocked by switch 27. In addition, the output of routing switch
11 at node 28 is shorted to ground, and hence, the common-base
transistor 23 in port terminal switch 29 is non-conducting, which
provides additional isolation. See page 3 of Appellant's
specification.
Claim 1 is representative of Appellant's invention and is
reproduced as follows:
1. A transfer switch having a test signal input and first and
second ports, said transfer switch comprising:
a first routing switch having a routing switch input for
receiving said test signal input and first and second outputs,
each output being connected to said routing switch input by a
first switching element and each output being connected to ground
by a second switching element; and
first and second port termination switches connected to said
first and second outputs, respectively, of said first routing
switch, each termination switch comprising a common-base
transistor.
33
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