Appeal No. 2002-0510 Page 2
Application No. 09/139,309
that can penetrate and damage electrical circuits and equipment. Such voltage
transients produce large voltage spikes with high peak currents, i.e., overvoltage.
(Spec. at 1.)
According to the appellants, variable voltage materials are used commonly in
variable voltage protection devices to short overvoltage transients to ground. (Appeal
Br. at 3.) Such materials initially display a high electrical resistance. When an
associated device experiences an overvoltage transient, its variable voltage material
changes to a low electrical resistance, thereby directing excess current harmlessly to
ground. After the transient has passed, the material reverts to the high electrical
resistance. (Id.)
The appellants explain that the key operational parameters of a variable voltage
material are "response time," "clamp voltage," and "switch voltage." Response time is
the time it takes for the material to switch from high resistance to low resistance. (Id.)
Clamp voltage is the voltage at which the material limits a voltage surge. (Id. at 2-3.)
After the material switches to a low resistance, it ensures that the circuit or equipment
being protected will not be subjected to a voltage greater than the clamp voltage.
(Spec. at 2.) Switch voltage is the voltage at which the variable voltage material will
switch under surge conditions from high resistance to low resistance. (Appeal Br. at 4.)
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Last modified: November 3, 2007