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From Extracts, Communications Instructions
USN 1944, Marine Operational Training Group-81, MCAS Edenton,
N.C.
2121. A call sign is a group of
letters, numerals, or both, assigned to an activity to
represent that activity in the headings of
messages.
a. An individual call sign is a
call sign representing a single station, unit, command, or
other activity.
b. A collective call sign is a
single call sign representing two or more individual call
signs.
c. A net or group call
sign is a collective call sign covering all stations in a net
or group on the same frequency.
d. An indefinite call sign is one
which indicates no specific station and may represent any
station or any of a group of stations.
2122. U.S. Navy call signs are
assigned in accordance with the following plan:
a. Three-letter N calls represent
shore radio stations. A three-letter N call with a
numeral preceding or following represents a subassignment
within the area controlled by a major shore
station.
b. Four-letter N calls represent
ships. A portable station under the control of a naval
vessel has the call of the vessel with a numeral
added.
c. Letter-numeral-letter calls
denote units which have facilities for answering calls
direct.
d. Four-letter pronounceable calls,
other than those starting with N, represent shore stations or
units which do not have facilities for answering calls
direct.
e. Five-letter N calls represent
aircraft.
f. Call signs consisting of two, three,
or four numerals plus a letter are assigned by blocks to
aircraft.
g. Other combinations of letters,
numerals, or both are used as visual call signs for
ships, aircraft, tactical organizations, and task
forces.
h. Further information regarding assignment
of call signs will be found in the U.S. Navy Call Sign
Book.
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