APPENDIX A
MIL-HDBK-162A
Volume 1 of 2
15 December 1965
EXPLANATION OF THE NAVY TYPE DESIGNATION SYSTEM (cont'd)
Class No.
Material
79
LF Underwater Sound Projector (10 kc or below).
83
Frequency Control Systems.
84
Control by Radio.
85
Interference Reduction.
87
Experimental Superfrequency Equipment.
88
Instrument Landing Equipments.
89
Radio Recognition and Identification Devices.
90
Visual Signalling Apparatus (This classification for type number assignments only).
EXPLANATION OF THE NAVY MODEL LETTER SYSTEM
Items in the Navy Model Letter System are designated by two or three basic letters - sometimes supplemented by
prefix or suffix letters and/or numerals.
Equipments identical in all respects and purchased from the same contractor bear the same model designation.
Additional equipment obtained for service use by additional purchase is designated by a numeral following the original
model letters. For example, on subsequent orders for the Model TAQ transmitting equipment, the equipment is identified
by the designations TAQ-1, TAQ-2, etc. Additionally, if after acceptance by the Navy Department, the Bureau of Ships
authorizes a modification of the equipment, a lower case alteration letter is assigned to follow the model letters. For
example, if a Model TAB-1 transmitter is modified after delivery by the addition of a harmonic suppressing circuit or unit,
the model designation would be changed to a TAB-1A. An additional modification of the TAB-la or a modification of the
TAB-1 differing from the "a" modification, would be indicated by "b" and the equipment designated known as TAB-lb.
Equipments of an experimental nature are assigned model letters beginning with "X" if manufactured by a Naval
organization (e.g., XA, XB, etc.), or with "CX" if manufactured by a commercial company (e.g., CXA, CXB, CXAA, CXAB,
etc.)
Preliminary models of equipments, subsequently to become the property of the Navy, as required by the terms of a
contract or similar authorization are given an "X" prefix letter, separated from the basic designation by a dash. The
preliminary (test) model of "Model TBU" was therefore designated 'Model X-TBU." The Navy Model Letter series is shown
in the following table.
NAVY MODEL LETTER SYSTEM
Model Letter
Model Subseries
Type Equipment
Remarks
Series
Airborne Radio and Radar Equipment
All new assign-
ments to Airborne
A --------------
----------------
Equipments shall
AB---------- --
Airborne IFF
be in the "AN'"
AI--------------
Airborne Radar Intercept
(Army-Navy) No-
AM------------
Airborne Radio Transmitting
menclature System
----------------
and Receiving.
AR----------- -
Airborne Radio Receiving.
AS---------- --
Airborne Search Radar.
AT-------------
Airborne Radio Transmitting.
AY----------- -
Airborne Radar Altimeters.
B --------------
----------------
Ship-Shore IFF Equipment.
C--------- -----
CX ------------
All Commercial Experimental Equipment.
D --------------
----------------
Ship-Shore Radio and Radar Direction
----------------
Finding Equipment.
1A-13
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