The Federal Circuit Interprets the Meaning of “A” in Patent Claims

The Federal Circuit Interprets the Meaning of “A” in Patent Claims

Photograph of clothespins hanging upside down on a clothesline, the clothespins resemble the letter "A".

Salazar v AT&T Mobility LLC, No. 2021-2320, 2021-2376 (Fed. Cir. April 5, 2023)

In recent years, patent drafters have omitted wordy phrases like “at least one” and “one or more” in order to prioritize readability, but a recent decision from a US court may reverse that trend. On April 5, 2023, the U.S. Court of Appeals for the Federal Circuit (“the Federal Circuit”) contemplated the meaning of the word “a” to determine whether a patent claim requiring “a microprocessor” meant one single microprocessor, or more than one. The Federal Circuit found that the use of the term “said microprocessor” later on in the same claim supported the interpretation of only one microprocessor.


Joe Salazar was the inventor and owner of U.S. Patent No. 5,802,467 (“the 467 Patent”), which described technology for wireless and wired communications. In 2016, Salazar sued HTC Corporation, alleging the HTC One phone infringed the claims of his patent.[1] A jury ultimately found that HTC Corp. did not infringe the ‘467 Patent, but did not make a decision on whether the ‘467 Patent was valid.

In the present decision, Mr. Salazar alleged infringement of the ‘467 Patent again by the same products, but this time sued AT&T for selling the phones. Independent claim 1 of the ‘467 Patent stated:

  1. A communications, command, control and sensing system for communicating with a plurality of external devices comprising:

a microprocessor for generating a plurality of control signals used to operate said system, said microprocessor creating a plurality of reprogrammable communication protocols, for transmission to said external devices wherein each communication protocol includes a command code set that defines the signals that are employed to communicate with each one of said external devices;

a memory device coupled to said microprocessor configured to store a plurality of parameter sets retrieved by said microprocessor so as to recreate a desired command code set, such that the memory space required to store said parameters is smaller than the memory space required to store said command code sets;

a user interface coupled to said microprocessor for sending a plurality of signals corresponding to user selections to said microprocessor and displaying a plurality of menu selections available for the user’s choice, said microprocessor generating a communication protocol in response to said user selections; and….

The District Court characterized the issue as whether the claims required one microprocessor that was capable of performing all of the recited functions (“creating”, “retrieving”, “generating”), or more than one microprocessor performing the functions separately. The District Court interpreted “a microprocessor” to mean at least one microprocessor capable of satisfying all of the functions listed for “said microprocessor”. As a result, the jury found that the AT&T products did not infringe the ‘467 Patent.

On appeal, Mr. Salazar argued that the District Court erred in its interpretation of “a microprocessor” and that the correct interpretation would be “one or more microprocessors, any of which may be capable of performing each of the functions recited”. This interpretation would allow for one microprocessor capable of performing one claimed function, and another microprocessor capable of performing a different claimed function, even if there was no single microprocessor that could perform all of the functions.

Using Indefinite Articles in Patent Claims

The Court of Appeals for the Federal Circuit found that the District Court had correctly interpreted the language of claim 1, and affirmed the non-infringement decision. The Federal Circuit acknowledged that the word “a” was an indefinite article that usually means “one or more” in open ended patent claims containing the transitional phrase “comprising”. However, the Federal Circuit relied on precedent to note that an exception to this general rule only arises when the language in the claims, specification or prosecution history dictates so.

In this case, the Federal Circuit interpreted “a” in “a microprocessor” to mean only one microprocessor because of the repeated use of “said microprocessor” later on in the patent claim. Each time the claim used “said microprocessor”, it referred back to the originally identified microprocessor, which prevented the interpretation of multiple microprocessors working together to achieve the described functionality.  The Federal Circuit found that rather than supporting an exception to the general, this use invoked a singular meaning for “a”, and interpreting it any other way would ignore the meaning of the word “said”.

The Federal Circuit also rejected Mr. Salazar’s argument, specifically quoting Varma to state “[f]or a dog owner to have ‘a dog that rolls over and fetches sticks,’ it does not suffice that he have two dogs, each able to perform just one of the tasks”. As a result, the Federal Circuit concluded that the ‘467 Patent was not infringed because HTC’s product used multiple processors and no single processor was capable of performing all of the claimed functions.


This unfavourable result for Mr. Salazar could have been avoided if the patent claims had been drafted to explicitly state that the functionalities could be divided between one or more processors. For example, the claim could have stated “one or more microprocessors, wherein the one or more microprocessors are collectively capable of generating…, creating…., retrieving…”. Going forward, we are likely to see more of this type of verbose claim drafting in order to prevent ambiguity and unfavourable interpretation. For more information on U.S. proceedings or to obtain IP protection for your assets, please contact a patent professional at PCK Intellectual Property.


[1] Salazar v. HTC Corp., No. 2:16-cv-01096, 2016 WL 11577368 (E.D. Tex. Oct. 5, 2016).

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