a. All Federal departments and agencies shall use the terms and definitions contained herein. Only after determining that a term or definition is not included in this document may other sources be used. The Legend table on page xi is provided to assist users in determining the documentary source of the definitions where multiple definitions are included for a single term.

b. All terms are listed alphabetically. Terms containing numerals are alphabetized as though the numbers were spelled out; thus, "F1A-line weighting" will appear in the "F" portion of the alphabet between the terms "FOC" and "footprint," since it is pronounced "F-one-. . ." and "144-line weighting" will appear in the "O" portion of the alphabet, alphabetized as "one-forty-four line. . . ." For user convenience, exceptions to the rule are taken for entries comprising numerically sequential terms, e.g., "digital signal 0," . . . "digital signal 4," which are grouped numerically following the "digital signal" entry.

c. An abbreviation for the term name often appears in parentheses following the term name. In some cases, this abbreviation is properly an acronym, and is thus labeled. [As a general rule of thumb, an acronym is an abbreviation that constitutes a word that can be (or usually is) pronounced.] The list of abbreviations and acronyms appears at the end of this glossary.

d. Terms with more than one definition have numbered definitions. Generally, definition number "1" contains the most frequently used meaning of the term. Notes and cross-references are placed with the appropriate definition(s). Three types of cross-references are used: "Synonym," "See," and "See also":

(1) When terms are synonymous, the definition is placed under only one of the term names, generally the preferred name. Synonyms are listed for cross-reference purposes only. The other term name entries contain only a "Synonym" listing (and other cross-references, where appropriate); i.e., the definition for synonymous term names is not repeated. Terms labeled "Colloquial synonym" are in occasional informal use, but typically are semantically inexact, causing confusion, or may border on slang.

(2) "See" is used where an undefined term name is entered as a cross-reference only to direct the reader to a related term (or terms) that is (are) defined in the glossary.

(3) The "See also" cross-reference is used to identify term names that are related or contrasted, to amplify the reader's understanding of a family of terms.

e. Term names that are semantically incorrect, that have been replaced by recent advances in technology, and that have definitions that are no longer applicable, are designated as "deprecated." Reference is made to new terms or to new definitions, where applicable.

f. The telecommunications terms included in this glossary either are not sufficiently defined in a standard desk dictionary or are restated for clarity and convenience. Likewise, combinations of such words are included in this glossary where the usual desk-dictionary definitions, when used in combination, are either insufficient or vague.