US Tri-Service Designation System Electronic Equipment

Introduction

In 1962, the US Military adopted the so-called "Tri-Service" designation system, which is still used today. Under the system, the three services (USAF, USN and USMC) were to use common designations for aircraft, guided missiles and electronic equipment. The conventions are described in the DEPARTMENT OF DEFENSE PUBLICATION 4120.15-L and are officially known as the MDS (MISSION, DESIGN, AND SERIES SYSTEM). Below are the details of the designation system for electronic equipment:

General Format

A typical designation for electronic equipment has the following format:


with X for an arbitrary letter and the hash-mark for an arbitrary digit. Not all letters or digits are necessarily used, and AN/ is optional. All characters have a special signification, according to their position in the designation:

Joint Service Indicator

AN is the optional joint service indicator, seperated from the rest of the designation by a slash. The numbers of the sections below correspond with the numbers in the figure above.

Platform / Installation

Indicates the nature of the platform on which the equipment is installed.


Platform / Installation

Prefix	Platform
A	Airborne (Piloted Aircraft)
B	Underwater Mobile (Submarine)
C	Air Transportable
D	Pilotless Carrier
F	Fixed (Ground)
G	General Purpose Use
K	Amphibious
M	Ground Mobile
P	Portable
S	Water
T	Ground Transportable
U	General Utility Assemblies
V	Ground Vehicular
W	Water Surface and Underwater Combination
Z	Piloted and pilotless airborne combination

Equipment Type

Indicates the type or nature of the equipment.

Equipment Type

Prefix	Type
A	Infrared or Invisible Light
C	Carrier (Wire)
D	Radiac
E	Nupac
F	Photographic
G	Telegraph or Teletype
I	Interphone or Public Address
J	Electromechanical or Inertial Wire Covered
K	Telemetering
L	Countermeasure
M	Meteorological
N	Sound in Air
P	Radar
Q	Sonar and Underwater Sound
R	Radio
S	Special Types, Magnetic Combination of Types
T	Telephone
V	Visual or Visible Light
W	Armament
X	Facsimile or TV
Y	Data Processing

Purpose

Indicates the primary task for which the equipment was designed.

Purpose

Prefix	Purpose
A	Auxilary Assemblies
B	Bombing
C	Communications
D	Direction Finding, Recon, and/or Surveillance
E	Ejection and/or Release
G	Fire Control or Light Finding
H	Recording / Reprocucing
K	Computing
M	Maintenance or test assemblies
N	Navigational Aids
Q	Special or Combinations of Purposes
R	Receiving / Passive Detection
S	Detecting and/or Range Bearing, Search
T	Transmitting
W	Automatic Flight / Remote Control
X	Identification and Recognition
Y	Surveillance and Control

Design Number

Supposedly in sequential order, it indicates the model of the vehicle within the basic mission category

Series

Indicates (alphabetically) major modifications to the original design, which is indicated by the A. I and O are usually skipped in order to avoid confusion with the 1 and the 0.

Configuration Number

Indicates a minor modification.

Example

The AN/ALQ-131B is a Joint-Service, airborne countermeasures device for special purposes, model nr.131, modification B.