AN-/Citable Version

Due to technical limitations, this article uses an unusual title. It should be called  AN/ prefix.

Most U.S. military electronics equipment has designations in the form AN/ABC-99, in which AN/ (note slash) is purely an identification for a designation system, not an abbreviation. This always-evolving system began as the Joint (Army-Navy) Electronics Type Designation System. Information security equipment under the control of the National Security Agency belongs to the TSEC/XYZ series, except certain of the letters in the AN/ system are reserved for NSA use.

While the designation system codes are quite complex and still contain special cases, the basic structure is:

• First letter: Where or how is it installed?
• Second letter: What kind of information or energy does it handle?
• Third letter: What does it do with the information or energy?

The next numbers indicate a main model number within the series, followed by a bewildering and inconsistent set of version levels, alternate configurations, etc. Sometimes, what may seem an incremental improvement gets an entirely new model number, while a radical change may get a version change only. In other words, grasp the general principles of the system, but know that you will have to examine a specific system to understand its designation nuances.

So, in each of the following three systems, the differences are in the first letter, which tells the kind of platform (aircraft, ship, ground-transportable) that carries it.

• AN/APY-2 is an airborne tracking radar, which is aboard the E-3 Sentry Airborne Warning and Control System (AWACS) aircraft
• AN/SPY-2 is a shipboard tracking radar, in this case the ballistic missile defense radar on ships equipped with the AEGIS battle management system
• AN/TPY-2 is a ground-based ballistic missile defense radar, which is moved from operating location to location by truck or cargo aircraft

The P in the second position means they radar energy, while the Y in the third position shows that they are combined target tracking and weapons fire control system. "Fire control" does not mean that the system is the only radar involved in guiding weapons for the application of the system; the three systems here are for long-range detection, and either guiding weapons-launching aircraft to the target or directing the initial flight of missiles. For example, the AN/SPY-2 detects a target, guides a RIM-156 Standard SM-2 missile to it, but, for the final attack of the missile, an AN/SPG-62 radar "illuminates" the target with energy that will be detected by the terminal guidance radar receiver inside the missile. See the specific AN/SPY-2, RIM-156 Standard SM-2, and AN/SPG-62 articles for further detail.

A somewhat more complex example, AN/APG-63 (V)3 is the airborne radar in the F-15 Eagle fighter.

• A in the first position means airborne
• P in the second position means radar
• G in the third position, in this case, means weapons control
• The first suffix part, (V) not only shows that it is a new version, but the (V) means it has a modular configuration, which can be changed in the field.
• Following the (V), the 4 is a version number. As a practical demonstration that the number following the three letter code can be fairly arbitrary, the AN/APG-63 (V)4 not only replaces the (V)3 on the air superiority F-15, it also replaces the AN/APG-70 on the ground attack F-15E Strike Eagle.

In contrast, a simple letter suffix means that the system is not field reconfigurable.

• AN/ALR-56 is a software-controlled radar warning receiver. Its AN/ALR-56C model is on F-15 series fighters, but the AN/ALR-56M model is used on F-16 Fighting Falcon fighters and C-130 Hercules transports.

Designation system codes

In the table below, only current codes are used. Animal-carried systems are no longer designated: the air-transportable pigeon loft and message center is no longer in service.

RR types in current use

Letter	Installation	Information	Function
A	Manned aircraft	Invisible Light, Heat Radiation	Auxiliary equipment
B	Submarine	(formerly pigeon)	Bombing
C	NSA reserved	Electronic carrier wave	Communications
D	Pilotless aircraft (UAV, drone)	Ionizing radiation	Direction finding, surveillance
E	-	Laser	Ejection
F	Fixed ground installation	Fiber optics	-
G	Ground mobile	Teletype or telegraph	Fire (i.e., controlling the firing of weapons) or searchlight control
H	-	-	Recording
I	-	Intercom, interphone, public address	-
J	-	Electromechanical	-
K	Amphibious	Telemetry	Computing
L	-	Countermeasures	-
M	Self-propelled ground	Meteorological	Maintenance
N	-	Sound in air	Navigation
O	-	-	-
P	Portable (personal)	Radar	-
Q	-	Underwater sound	Special
R	-	Radio	Receiving or passive detecting
S	Ship	Special	Active detecting, search
T	Ground transportable; not usable while moving	Telephone	Transmitting
U	Utility/combination	-	-
V	Vehicle	Visible light	-
W	Water	Miscellaneous weapons	Remote control
X	-	Television or facsimile	Identification or recognition
Y	-	Computing	Target tracking, fire control
Z	NSA reserved	Secure (NSA reserved)	NSA reserved

AN/ designations and system architecture

Various pieces of equipment, which have AN/ designations, are best understood when it is realized that they fit into larger architectures, or transitions between architectural generations. For example, there is an obsolescent tactical communications architecture called TRI-TAC, which, loosely speaking, is being replaced by Warfighter Information Network–Tactical (WIN-T). Two major components of TRI-TAC are the AN/TTC-39 and Mobile Subscriber Equipment switches; the latter, for administrative reasons, does not have a full AN- designation. Some individual pieces of equipment, such as the AN/TTC-56 switch, are transitional between architectures such as TRI-TAC and full WIN-T.

Examine, however, the AN/TTC-39 designation. Its initial "T" indicates a transportable system that has to stop to operate. This specific piece of equipment requires large aircraft and trucks to transport. The second "T" shows that its major application is telephony. "C" in the third position shows that it is a communications system. The same prefix applies to the AN/TTC-56, but the implementation is quite different. The AN/TTC-56, for example, fits into intra-theater transport aircraft such as the C-130 Hercules, can be lifted by helicopter, or moved (with its electrical power generator) by a pair of HMMWV light wheeled utility vehicles.

These formal designations, in practice, are complemented by informal names. AN/TTC-39 switches, for example, are called "Tick 39", while the AN/TTC-56(V)1, officially the Single Shelter Switch, is called the triple-S by Army personnel.