More Details: The patent in suit was U.S. 6,628,771. Several independent claims included the following element: "circuitry to recognize a first signal with a duty cycle or cadence coupled with frequency and level indication of a call waiting SAS signal." During claim construction, the parties focused on whether or not "circuitry" included " 'software based implementations', e.g., programmable microcontrollers."
After examining two Federal Circuit decisions which involved the term "circuitry" (Linear Tech. and Abacus Software), the Court found that neither addressed this precise issue. The Court decided that even if "circuitry" wouldn't usually be understood by a POSITA to cover software based implementations, it was in this case. Here, the specification clearly described the function of the claimed "circuitry to recognize" as being performed by a microcontroller, and more specifically by a programmed microcontroller.
[T]he principal function of [microcontroller 412] is to receive call progress signals, specifically for the preferred embodiment of the present invention, it is the call progress signal (SAS) alerting signals for CW and DCW.The Court also noted that interpreting circuitry so as to exclude a microcontroller would exclude the preferred embodiment. A claim construction which excludes the preferred embodiment requires evidentiary support (Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582 (Fed.Cir.1996)), and there was no such evidence presented here.
[T]he microcontroller 412 is programmed with timing algorithms, which provide the flexibility for recognition of CW and a plurality of DCW signals.
In summary, the Court found that the patentees had, through the written description and prosecution history, redefined "circuitry" to cover a microprocessor or microcontroller programmed to perform the claimed function.
My two cents: A mere footnote in the decision also noted that the spec contained broad language suggesting that "circuitry" covered software implementations: “[W]hile the disclosed embodiments of the present invention utilize programmed processors, and special-purpose integrated circuits, and digital processors these devices can be implemented using discrete devices, or any analog or hybrid counterpart of any of these devices." Since the Court put this in a footnote, and focused mostly on the other stuff mentioned above, I'm not sure that this broad language alone would be enough to move software into the area of coverage.
Presumably the patent drafter was focused on covering a software implementation, since the only embodiment described in detail was a software implementation. If so, calling it "circuitry" is a really odd way to go about it. By doing so, the patentee virtually guaranteed a fight with any defendant that used software to implement the function – which is exactly what happened here. Why not write a claim that more clearly covers the preferred embodiment?
On the other hand, maybe the patent drafter found a really clever way to cover both a hardware implementation and a software implementation with a single element. You might think means-plus-function is the perfect technique to do just do this, but it's not. Invoking § 112 ¶ 6 in the software realm heightens the disclosure requirement considerably. Imagine that instead of simply saying something like "suitable structures for fastening include a screw, a rivet, and a bolt," you had to explain in some detail how each of these items worked in order to claim "means for fastening." That's what the Federal Circuit requires when the structure performing the function is a processor: disclosure of a specific algorithm for each claimed function. (See Aristrocrat v. IGT.)
The patentee won an important victory at claim construction, since the accused infringer's device did use software. But you'll see in a future post that the patentee lost the war on infringement.