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Index to the U.S. Patent Classification System

Explanation of Data

The following symbols and abbreviations are used in this Index:
A ... Z :
An "Alpha" designation following the official numeric subclass identifies an unofficial subclass; i.e., a grouping of patents selected out from an official subclass by an Examiner and then made an indented subclass under the official subclass, usually for purposes of further breaking down a concept. Topics not specifically selected out are left in a residual subclass, designated with the alpha R. Unofficial subclass groupings are used in the Examiners' files, and they are not available in the Public Search Room.

For example, in Class 273, subclass 120 is an official subclass, subclass 120A is an unofficial "Alpha" designation subclass, and subclass 120R is a residual subclass. Please note that in the Manual of Classification, where "Alpha" designation subclasses exist for an official subclass, only the alpha designation subclasses are listed.

Ctg :
"Containing" may be abbreviated "ctg" in long chemical phrases.

D :
A class number preceded by the letter D identifies a Design Class.

The letters "DIG" followed by a number identify an unofficial collection of patents (i.e., a "digest") based on a concept which relates to a class but not to any particular subclass of that class. For example, Class 123, DIG 12, is a collection of hydrogen-fueled engines in Class 123, Internal Combustion Engines. Digests have been created over the years by Examiners to facilitate their searches within the arts or technologies under their jurisdiction. Digests are unofficial collections and are not available in the Public Search Room.

The letters PLT identify the Plant Class.

TM :
The letters TM identify a trademark name. These names have been included where a particular field of search could best be suggested by such.

+ :
The plus sign following a subclass indicates that the entry includes that subclass and all subclasses indented thereunder (see the Manual of Classification for classification schedules).

X-art :
Cross-reference Art Collections may be described in the text as "X-art" collections. These are digests (see the "DIG" entry, above) for which written definitions have been provided.

* :
A subclass number followed by an asterisk identifies a Cross-Reference Art Collection (see the "X-art" entry, above).

Discussion of Usage

The Index to the U.S. Patent Classification System, referred to hereafter as the Index, is intended as an initial means of entry into the classification system. The Index should be particularly useful for those lacking experience in using the classification system and those unfamiliar with the particular terminology under consideration. It is an alphabetical list of subject headings referring to specific classes and subclasses of the classification system.

There are continual changes in the classification system. New classes and subclasses are established due to new developments in science and technology, and old classes and subclasses are abolished when rendered obsolete by technological advances. In addition, changes to classes and subclasses may result from an effort to streamline and update the definitions. This edition is current as of the date indicated at the top of the web pages.

A list of utility and design class titles is available in the Manual of U.S. Patent Classification. Searchers may find it useful to scan the titles for topics which may be of interest to them.

As a first step in locating a field of search, the searcher should look in the Index for the term that best represents the subject matter of interest. If a match is not found, the user should look for terms of approximately the same meaning, for terms of either broader or narrower scope, or for terms which represent a different approach to the subject; i.e., the essential function or effect of the device or the use or application to which the device or composition of matter is put. On finding the identifying numbers of possibly pertinent classes and subclasses in the Index, the user should refer to the Manual of Classification and ascertain, from among the existing choices, the precise classification (that is, the class) of the subject of interest. The user should start with the first "mainline" subclass; i.e., any subclass depicted without indents and presented in all capital letters, in the selected class, and proceed from one mainline subclass to another until the first one is found that appears to include the subject matter being investigated. Next the user should scan all of the subordinate subclasses indented one place to the right under the selected mainline subclass until the first one is found that indicates inclusion of the subject matter being investigated. Using this same technique, the searcher should scan the subclasses indented one additional place to the right under the previously identified subordinate subclass until no further levels of indentation are available. Whenever doubt arises as to the proper subclass choice, the user should consult the classification definition for the class under study. The Classification Definitions supplement the Manual of Classification in that they contain detailed definitions and illustrations of the kind of subject matter that can be found in each class and subclass, the lines of distinction among classes and subclasses, and references to other classes and subclasses having related subject matter.

Subject headings in the Index are not an alphabetical inversion of the Manual of Classification. They are a subjective determination of relevant terms, phrases, synonyms, acronyms, and occasionally even trademarks that have been selected over the years as the best identifying description of products, processes, and apparatus of patent disclosures.

The Index contains product-related entries, whereas the Manual of Classification is descriptive or nonspecific. For example, the Index entry for phonograph record molding apparatus is reflected in the Manual of Classification as a "press forming apparatus having opposed press members." Some effort has been made to index current vocabulary usage when the classification system may contain technically general language; e.g., "water bed" or "air mattress" for the concept "fluid-containing mattress."

The Index is arranged alphabetically with subheadings that can have four levels of indentation. A complete reading of a subheading includes the title of the most adjacent higher heading, and so on until there are no more higher headings. Some headings will reference other related or preferred entries with a "(see...)" phrase. They may reference the notes to the Classification Definitions when these notes are particularly detailed or lucid on important distinctions not easily captured in the abbreviated entries of the Index.

While measures have been taken to provide accurate and complete information in these web pages, errors and omissions may occur.

For a more complete description of the U.S. Patent Classification System and the procedures used to classify patents within the system, please consult the Examiner Handbook to the U.S. Patent Classification System.


Questions regarding these reports should be directed to:

U.S. Patent and Trademark Office
Information Products Division
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Washington, DC 20231

tel: (703) 306-2600
FAX: (703) 306-2737
email oeip@uspto.gov

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Last modified 24 August 2000