District court, in concluding that “circuit” limitations in claims for computerized switching systems are means-plus-function limitations, erred by relying on single word “circuit” rather than examining limitations as whole, since every use of term in asserted claims includes additional adjectival qualification that further identifies sufficient structure. A claim term that does not use “means” will trigger the rebuttable presumption that § 112, paragraph 6 does not apply. The presumption can collapse when a limitation lacking the term “means” nonetheless relies on functional terms rather than structure or material to describe performance of the claimed function. To help determine whether a claim term recites sufficient structure, the court must examine whether the claim term has an understood meaning in the art. Thus, the threshold issue for all the limitations involved in the “circuit” is whether the term itself connotes sufficient structure to one of ordinary skill in the art to perform the functions identified by each limitation. While the court did not find it necessary to hold that the “circuit” by itself always connotes sufficient structure, the term “circuit” with an appropriate identifier such as “interface,” “programming,” and “logic,” certainly identifies some structural meaning to one of ordinary skill in the art. The term “circuit” is defined as “the combination of a number of electrical devices and conductors that, when interconnected to form a conducting path, fulfill some desired function.” In light of this definition, it is clear that the term “circuit” by itself connotes some structure. (Apex Inc. v. Raritan Computer Inc., 66 USPQ2d 1444, CA FC, 4/2/03).