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Classification of the subject matter of an international application

Q: I am the head of a newly formed team of researchers. We have just invented an electronic component, and are considering filing an international patent application. I am therefore trying to familiarize myself with patent documentation. I have studied an international search report that was published with an international application, and wondered if you could explain the significance of the symbol that appears in Box A of the international search report ("Classification of subject matter") (as well as in the top left hand corner of the front page of the pamphlet) and let me know how I can find out what that particular symbol means. (The symbol given in respect of the application reads: "IPC 7 HO4N5/455".)

A: The symbol referred to in the international search report (ISR) (and on the front page of the pamphlet) is a classification symbol which describes the technical field to which the invention relates, according to the International Patent Classification (IPC). In some ISRs, there may also be a symbol according to a national classification system.

Such classification symbols are included in published patent documents, whether they be patent applications or granted patents, for the purposes of orderly (classified) arrangement of those documents, thereby permitting a search and, thus, retrieval of documents relating to distinct technical subject matter. Such retrieval is required by patent-issuing authorities, potential inventors, research and development units, and others concerned with the application or development of technology, in order to examine any relevant prior art. For example, in the case of an international application, once the International Searching Authority has determined the classification symbol(s) that will be attributed to an invention, they can use that/those symbol(s) to search any prior art.

The IPC is a hierarchical classification system comprising sections, classes, subclasses and groups (main groups and subgroups) (in descending order of hierarchy). It is based on the "Strasbourg Agreement Concerning the International Patent Classification"—an international multilateral treaty administered by WIPO which entered into force in 1975—and was established so that a single classification system could be used in a large number of countries.

To find out the technical field or fields into which an application has been classified, interested parties can consult the IPC. The IPC is available on the WIPO website or is available on paper (this version consists of ten volumes and is available in English or French) or on the "IPC: CLASS" CD-ROM (this version contains all editions of the IPC in English and French and certain editions in other languages). The paper version and the CD-ROM can be obtained from the Marketing and Distribution Section at WIPO:

The following part explains the different components of the classification symbol which has been attributed to the application to which you refer.

The number "7" following the letters IPC indicates that the symbol has been taken from the seventh edition of the IPC, which entered into force on 1 January 2000 (the IPC is updated to take into account various changes, such as changes in technology, and is republished in a new edition every five years). Any patents or patent applications that were searched prior to January 2000 carry an earlier IPC edition number.

The rest of the classification symbol denotes the section, class, subclass and group, as defined below. Each section, class, subclass or group symbol is followed by a title, which qualifies the nature of the subject matter; the further down the hierarchy of the IPC is being consulted, the greater the technical detail is given in the title of the category. That title is not given in the ISR, but can be found by consulting the IPC itself. Note that the seventh edition of the IPC consists of 8 sections, 120 classes, 628 subclasses and almost 69,000 groups.

1) Sections

The IPC divides all technological fields into eight sections designated by one of the capital letters A through H. The sections and their respective titles are:

A Human necessities

B Performing operations; transporting

C Chemistry; metallurgy

D Textiles; paper

E Fixed constructions

F Mechanical engineering; lighting, heating, weapons, blasting

G Physics

H Electricity

The invention referred to in the question falls in section H: "Electricity."

2) Classes

Each section is subdivided into "classes." The class symbol consists of the section symbol followed by a two-digit number. The invention has been classified into Class H 04. That class is entitled: "Electronic communication technique."

3) Subclasses

Each class comprises one or more "subclasses." Each subclass symbol consists of the class symbol followed by a capital letter. The subclass symbol attributed to the invention in question is H 04 N, and is entitled: "Pictorial communication, e.g. television."

4) Groups

Each subclass is broken down into subdivisions referred to as "groups," which are either main groups or subgroups (a subdivision under main group). Each main group symbol consists of the subclass symbol followed by a one- to three-digit number, the oblique stroke and the number 00. Subgroups form subdivisions under the main groups and consist of the subclass symbol followed by the one- to three-digit number of its main group, the oblique stroke and a number of at least two digits other than 00. The main group title defines a field of subject matter considered to be useful in searching for inventions; the subgroup title defines a field of subject matter, within the scope of its main group, considered to be useful in searching for inventions.

The invention has been given the classification symbol H 04 N 5/455, and has been classified under the subgroup entitled: "Demodulation circuits." As has been demonstrated above, that symbol comprises the combined symbols representing, in descending hierarchical order, the section, class, subclass and subgroup.

Box B of the ISR ("Minimum documentation searched") indicates which patent documentation has been searched, for example, the ISR might indicate that all documents classified in "H 04 N" have been searched.

Note that even if you work in a given technical field, your invention may be classified into a section different from the one that you expect. For instance, if an invention is in the field of drugs, despite the fact that the invention is linked to chemistry, it will be classified in Section A "Human necessities" and not in Section C "Chemistry; metallurgy."

To obtain more detailed information on the subdivisions of the IPC, you can review the Guide to the IPC, which explains the layout and use of the IPC symbols, as well as the principles and rules of the IPC and its interpretation, by clicking on "Guide" at: https://www.wipo.int/classifications/ipc/en/

Further information on the IPC is also available in the following documents: "General Information on the Seventh Edition of the International Patent Classification," the "Introductory Manual to the International Patent Classification" and "The First Twenty-Five Years of the International Patent Classification (1996)" at, respectively:

and a list of frequently asked questions about the IPC is available at:

Information on the IPC is also available on the WIPO website in French and Spanish at: