In Elbex Video, Ltd. v. Sensormatic Electronics Corp., No. 07-1097 (Fed. Cir. Nov. 28, 2007), the court held that the defendant failed to show a "clear and unmistakable" disavowal of a patent claim’s literal scope during prosecution of the patent. The disavowal in Elbex concerned whether, in a closed circuit television system, a signal for controlling cameras in the system had to go to a "monitor" rather than a "receiving means". The latter phrase appeared in the patent claim, but Sensormatic argued that Elbex abandoned any definition of "receiving means" broader than "monitor" — the receiving means and monitor were the same, it urged. But the Federal Circuit, unlike the district court, held the evidence of disavowal neither clear nor unmistakable. It also affirmed summary judgment on two of the three technologies that Sensormatic used in its CCTV systems. So the court affirmed in part and reversed in part and remanded.
Clear but mistakable doesn’t suffice. Nor does unclear but unmistakable. The disavowal must appear both clear and unmistakable.