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September 29, 1998

ONEAC CORPORATION, an Illinois corporation, Plaintiff,
RAYCHEM CORPORATION, a Delaware corporation, Defendant.

The opinion of the court was delivered by: GETTLEMAN


 On April 14, 1997, plaintiff Oneac Corporation brought a patent infringement action against defendant Raychem Corporation alleging that the defendant is infringing U.S. Patent No. 4,758,920 (the "920 patent"). The '920 patent, entitled "Telephone and Data Overvoltage Protection Apparatus," originally issued to Thomas McCartney on July 19, 1988, and was later assigned to plaintiff. The '920 patent relates generally to an overvoltage protection circuit for a pair of telephone lines and similar data communication channel. More particularly, plaintiff alleges that it relates to circuitry for filtering noise and transient voltage signals above data signals on the lines or channels. Defendant sells a telecommunication line overvoltage protection devices known as Tel Tec, which competes with plaintiff's product.

 On September 24, 1997, the court entered a stipulated order pursuant to which the parties agreed to stay all discovery other than that related to resolution of the interpretation of claim elements 1 and 11 of the '920 patent. The parties then filed cross motions for summary judgment limited solely to construction and interpretation of those claim elements.

 During the course of the instant litigation, the parties were also engaged in litigation in the United Kingdom over plaintiff's European Patent (UK) No. 0 338 107. That litigation involved the same inventions and substantially similar patent claim language. On May 7, 1998, Justice Hugh Laddie of the High Court of Justice, Chancery Division, Patents Court, Docket No. Ch 1997 O No. 1923, issued an opinion concluding that defendant's device infringes plaintiff's European patent. The parties submitted that decision to this court, *fn1" and the court ordered briefing on the issue of what, if any, preclusive effect that decision has on the instant case. All briefs have now been filed, and the cross motions for partial summary judgment pertaining to claim construction and infringement on claim elements 1 and 11 of the '920 patent are ripe for decision. For the reasons set forth below, the court construes the claim in accordance with plaintiff's arguments, but denies the cross motions for summary judgment on infringement.

 Both plaintiff Oneac and defendant Raychem sell telecommunications line overvoltage protection devices. These devices are used to prevent high voltage signals unintentionally carried on telephone lines from damaging expensive pieces of sensitive equipment, such as fax machines or computers. To understand the claim language at issue, it is necessary to discuss the relevant technology.

 Signals carried on telephone lines are a function of two variables. The first, voltage, or voltage potential, measures the peak magnitude of the signal being sent. The second, frequency, accounts for the number of complete cycles passed in a second. Some signals, d.c. signals, have no frequency component since they remain at a constant voltage. A.c. signals, on the other hand, do not have a constant voltage. Rather, the voltage rises and falls in a repeated cycle in the form of a sine wave. A cycle is completed when the voltage goes from an initial value of zero, to its maximum positive voltage, down to its maximum negative voltage, and back to zero. Frequency is measured by the number of cycles competed in one second. One cycle per second is known as 1 Hertz. Thus, a.c. signals are measured by their maximum voltage and their frequency.

 The telephone system requires the use of two distinct signals: (1) the ring signal and (2) the data signal. The ring signal's role is to make the phone ring. It has a low frequency and a high voltage. The data signal carries either the voices that one hears in the receiver or data sent to a fax machine or computer. This signal is high frequency and low voltage. Both of these signals are necessary for communication through telephone lines.

 Before plaintiff's invention was conceived, previous methods of protecting devices connected to telephones were created. These devices eliminated signals above a certain voltage. These methods of overvoltage suppression are not sufficient for fax machines and computers due to the sensitivity of these devices. Even a voltage less than that of the ring signal can damage this expensive equipment if the frequency of that signal is high enough. Thus, a new method of protection was needed to eliminate those high frequency signals with voltages greater than the data signal, but not necessarily greater than the ring signal.

 In the previous methods of voltage suppression, the protection circuits incorporated an electrical device known as a transient voltage suppressor (TVS). Ideally, this device operates as an open circuit when the voltage presented to it is below a predetermined threshold level and as a short circuit when the voltage is above the threshold level. In other words, when the signal is below the threshold voltage, the TVS operates like a cut wire through which the signal cannot pass. Meanwhile, above the threshold voltage, the TVS is ideally akin to a connecting wire through which signals can pass. The TVS is a useful tool for eliminating unwanted voltages, but not unwanted frequencies.

 Long present in the field of electrical engineering was also the concept of filters. By using devices known as resistors, capacitors, and inductors, a circuit designer could select which frequencies he or she wished to pass through the circuit. While several different types of filters have been implemented, the low pass filter is the only type relevant for this case. A low pass filter operates to attenuate the high frequency components of a signal. There are three common types of low pass filters: (1) RC filter, composed of a resistor and capacitor; (2) RL filter, composed of a resistor and an inductor; and (3) RLC filter, composed of all three devices. Incorporating a low pass filter into a device will eliminate high frequencies, but will allow high voltage signals at lower frequencies to pass.

 Neither the TVS nor the low pass filter could alone solve the problem of protecting sensitive equipment like fax machines or computers because they could eliminate signals only on the basis of their frequency or their voltage, not both. McCartney, the inventor of the '920 patent, devised a way to solve this problem by, in effect, combining the TVS and the low pass filter into one device. This was done by placing a TVS in series with the capacitor of an RC filter.

 When the voltage is within normal data signal range, the TVS acts like an open circuit. Consequently, the incoming signal is allowed to pass through the overvoltage suppression device with minimal degradation. When a voltage above this data range is encountered, the TVS acts like a short circuit allowing the signal to pass through it. However, the passed signal now encounters the capacitor of the RC filter. This component will pass high frequency signals, but will not pass low frequency signals. In other words, the capacitor acts as a short circuit at high frequencies and as an open circuit at low frequencies. Thus, the signal which is able to pass through the TVS must also have a high enough frequency to adequately pass through the capacitor. If a signal has a high enough frequency and voltage, it will pass through the TVS and the capacitor and thus will be removed by the overvoltage suppression device.

 By combining the TVS with the capacitor, plaintiff's device creates a switch for the low pass filter. When the incoming voltage reaches a predetermined level, the filter is "turned on" and high frequency components of the signal are attenuated. When the incoming voltage is below that level, the filter remains off. This solved the problem since it allowed the ring signal (high voltage, low frequency) and data signals (low voltage, high frequency) to pass through while eliminating the "transient signals" (high voltage, high frequency).


 There are two steps to a patent infringement analysis: proper construction of the asserted claim; and a determination as to whether the accused method or product infringes the asserted claim as properly construed. Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1581-82 (Fed. Cir. 1996). Thus, the court must first construe the claims before it can address whether either party is entitled to any form of summary judgment. As a result of the claim construction, the scope of plaintiff's patent rights are determined; only then can the court determine whether defendant's accused device reads on the claim elements in question.

 I. Claim Construction

 Both parties agree that it is only necessary to construe the third elements of the two independent claims: claim 1 and claim 11. These two claims are structurally and substantively similar. The discussion is focused primarily on the language of claim 1 because it has the broadest scope.

 The claim construction turns on one question: whether the claim language limits the scope of plaintiff's rights to devices that filter only when the predetermined threshold voltage has been reached. Plaintiff suggests an interpretation that reads the limiting language to apply only to the new filter apparatus, not the entire device. Defendant urges that the limiting language should be applied to the entire device, not merely one element of the claim.

 To construe the claims, the court first examines intrinsic evidence. Id. at 1582. The intrinsic evidence consists of the patent claims, the specification, and, if in evidence, the prosecution history. Id. If the intrinsic evidence alone is not sufficient, extrinsic evidence may be used. Id. at 1583. Extrinsic evidence is external to the patent and file history, such as expert testimony, inventor testimony, dictionaries, technical treatises, articles, and prior art not cited. Id. at 1584. Intrinsic evidence is preferred since it encompasses the materials in the public record. Id. at 1583. Therefore, if the intrinsic evidence alone resolves any ambiguity, it is improper to rely on extrinsic evidence. Id. at 1583.

 A. Claim Language

 Claims 1 and 11 of the '920 patent are "means-plus-function" claims. 35 U.S.C. ยง 112 P 6 enables the drafter of the claims to describe the function, or functions, performed by a means described in the specification. Means-plus-function claims must be construed to cover the structure disclosed in the specification and its equivalents. U.S. v. Telectronics, 857 F.2d 778 (Fed. Cir. 1988).

 Claim 1 reads:

1. An overvoltage protection circuit used with a pair of telephone lines comprising: first voltage clamping means for clamping voltage signals on said lines at a first predetermined voltage potential;
second voltage clamping means for clamping voltage signals on said lines at a second predetermined voltage potential; and
filter means responsive to said second voltage clamping means for filtering noise or transients signals from said voltage signals only when said voltage signals exceed said second ...

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