ELECTRIC RADIO Magazine
It was published in two parts, in the June and July 1995 issues. He hopes it helps you with these crazy nomenclature systems! If you pass it on, please add a credit line showing where/when it was first published in Electric Radio Magazine and written by Ray Mote.
World War Two Nomenclature Systems
1. Introduction: Like many, I struggled for years to gain an understanding of the nomenclature systems in use during World War Two. The "alphabet soup" on equipment data plates was incomprehensible without some sort of guide. With the help of information from friends like Robert Downs, Fred Chesson, Fred Raper, August Link, and others, I was able to put together a fair approximation of such a guide. 2. Overview: Three separate nomenclature systems were in use at the beginning of the war: the Army nomenclature system, the Navy model letter/type number system, and the Navy Mark/Mod system. These were joined in late 1942 by the new Joint Army-Navy (or "AN") System of nomenclature. The Army system featured the familiar SCR, SCM, SCS designators for systems, and BC, FT, HS, etc. for system components. The Navy used a series of two and three-letter designators for systems, while using a 5-digit type number for each system component. Both of these systems appear to have been in use since World War One or earlier. A second Navy system used Mark and Mod numbers for various ordnance items such as guns and shipboard fire control radars. In that system, there appears to have been no significant attempt to distinguish systems from components. Since so little of the Mark/Mod system applies to the material we encounter in collecting, it will not be discussed further. The Joint Army-Navy Nomenclature System was implemented to cope with systems intended for multiservice use or with potential for such use, thereby ending the confusion that resulted from a single system having two radically different nomenclatures assigned by the Army and Navy (such as the IFF system the Army called the SCR-515, also known as the Navy Model ABA). Of these four systems, only the AN system and the Navy Mark/Mod system have survived. 3. Army Nomenclature System: This system was developed for Signal Corps use at least as far back as World War I. Three-letter designators beginning with "SC" were used to denote complete systems, while one and two- letter designators were used for components. Only a few system designators were used:
The SCS designator was applied to groups of SCR-numbered sets comprising an extensive system, such as multiple radio sets employed in a ground-based fighter direction/control center. The SCR designator could be a single transmitting or receiving set, or a full set of both transmitting and receiving equipment. An additional designator, "RC" was used for subsystems or groups of accessories. This ranged from the RC-198 (the old familiar FL-8- A audio filter) to IFF systems which were intended to be used with ground or airborne radar sets carrying their own SCR designator. Each of these could have a suffix (as in the "SCR- 274-N"). Some early systems, such as the SCR-183 or 283 systems, carried a variant identifier between "SCR" and the number, such as "SCR-AL-183", "SCR-AN-183", etc. The designators for equipment components were:
4. Navy Nomenclature System: The Bureau of Steam Engineering, created in 1910, was initially given responsibility for Navy radio equipment. This continued after they were renamed as the Bureau of Engineering and lasted until they merged with the Bureau of Construction and Repair in July of 1940, emerging as the new Bureau of Ships (BUSHIPS or NAVSHIPS). Radio systems were assigned a two-letter model designation, with the first letter indicating the type of system and the second letter indicating the specific model. ("Model RA" would have been the first receiver). Separate components of a system were assigned type designators containing a two-letter prefix for the manufacturer and a four-digit type number. The prefix "SE" was used for Navy-built equipment, and commercial designs were assigned a two-letter manufacturer designator. The first two digits of the type number indicated the component type (46 - receiver, 52 - transmitter, etc.). Rapid growth during the period between wars soon made the old model letter and type number scheme obsolete. Lack of adequate detail obscures this process, but it appears that the new three- letter model designators and the five-digit type numbers were not implemented at the same time. As each equipment category reached the end of the available two-letter model series, they began using three-letter model designators for complete systems. Nomenclature for both the RU-1 and RAC receivers was assigned in December of 1931, with components of both units assigned five- digit type numbers. Unfortunately, with only a single letter available to indicate the model in the most heavily-used categories such as airborne receivers and transmitters, this system was also doomed. On the second contract for a specific model, the model designator was suffixed with "-1" (a second contract for the RAK would be designated as "RAK-1", a third contract as "RAK-2", etc.). Authorized modifications of the system by the Navy after delivery would result in addition of a lower-case letter suffix (such as RAK-1a, RAK-1b, etc.). Experimental equipment was assigned model letters beginning with "X" if manufactured by the Navy (XA, XB, etc.), or with "CX" if commercially manufactured (CXA, CXB, CXAA, CXAB, etc.). Preliminary models of equipments, intended to become the property of the Navy under the terms of a contract, were 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 new type number had a prefix for the manufacturer and five or six digits ("CRV-46151" for the Model ARB receiver). The list of manufacturers had long since outgrown the two-letter set and was rapidly using up the available three-letter designations. It was to grow well into the four-letter series by the end of the war. Five-digit type numbers were used for major pieces of a system (transmitters, receivers, control boxes, power supplies, etc.) and six digits for subassemblies and smaller parts. The first two digits were the "class" or general type of item, and the remaining digits indicated the specific component model. A modification to the basic design would result in addition of a hyphen and upper-case letter suffix ("COL-46159-A", etc.). Experimental components had an "X" added before the five digits ("X47101", etc.). Wartime developments forced a modification to the type number system. Classified equipment (radar, IFF, etc.) was assigned a type number with the usual two-digit class identifier and a three-letter suffix. Any component with an alphabetic suffix in the type number was instantly recognizable as classified equipment, and should have been more easily protected. Modified component type numbers were indicated with a numeric suffix ("CAY-50AEY-1", etc.) One further note: Generations of postwar typists unfamiliar with either the equipment or the model/type assignment principles have thoroughly fouled up the equipment lists they retyped.
5. Army-Navy Nomenclature: I've never seen a document that gives the exact date on which this system was implemented. We can infer the approximate date from initial nomenclature assignments, beginning with the AN/ARR- 1 (and AN/FRT-1) in late December of 1942. This was followed in January 1943 with assignments for the AN/ARR-2, 2X, and 3, as well as AN/ARN-1 and AN/CRT-1 components. Publications of the period made it abundantly clear that the presence of equipment with AN/-type nomenclature did not automatically mean that it was in fact used by both the Army and Navy! It only indicated that the type number was assigned in that system. System designators were formed from the prefix "AN/", three letters specifying the installation type, equipment type, and purpose, a hyphen, a numeric designator, and possibly a suffix to indicate a modification of the basic system. For example, an "AN/ARC-5X" would be a system under the Army-Navy Nomenclature System ("AN/"), it would be an airborne ("A") installation, radio equipment ("R"), used for communications ("C"). It would be the fifth such system assigned this nomenclature ("-5"), and it would have been modified for a different input voltage, phase, or frequency ("X"). In actuality, the AN/ARC-5X was intended for 14-volt DC systems rather than the normal 28-volt equipment, and it does exist. The table of system designators gives a full description of the possible combinations of three letters for the first part of the nomenclature. Modification letters for different input voltage, phase, or frequency were restricted to "X", "Y", "Z", "XX", "YY", etc., and were to be assigned in that order. Any other modification to the basic system was to be assigned a modification letter ranging from "A" to "W", "AA" to "WW", etc. Component nomenclature featured a one or two-letter prefix indicating the type of component, a hyphen, a number to indicate which component model was meant, and a possible modification suffix letter. For example, the R-2A was a modification of the original R-2 receiver design in the AN/ARR-3 airborne radio receiving system. One and two-letter prefixes are provided in the table of component designators. Note: NAVSHIPS 900,109 (Navy Type Number Book) uses "CO" for RF Cables and Transmission Lines, while CO-NAVAER 08-5Q-227 (Nomenclature List for Bureau of Aeronautics Aircraft Electronic Equipment) uses "CG" for this purpose. The Army version in War Department Pamphlet 11-3 (Signal Corps Equipment Security Classification List) also uses "CG". All three documents were published at about the same time, indicating the existence of at least some confusion about this system which was approaching its third birthday. It was possible to specify both the component and the major system for complete identification. For example, the R-2A full specification would have been "R-2A/ARR-3". This would be read as modification of receiver number two, part of (or used with) system AN/ARR-3. (The slant bar between the component portion and system portion of the description was read to mean "part of, or used with".) Some descriptions stop short of this point by giving only the three-letter generic designator after the slant bar. This was done to indicate that the component might be used with more than one system of that generic type (R-295/ARR, etc.). Experimental sets carried an experimental designator enclosed in parenthesis, composed of a two-letter originating agency designator, a hyphen, and the experimental model number. For example, AN/ARC-3 (XA-1) would designate airborne radio communications set number three, experimental model number one, built by the Aircraft Radio Laboratory. These two-letter agency designators are also shown in a table below. System Designators:
Experimental Sets: Originating Agency:
Component Designators:
6. Confusion Factors: There are a number of aspects of the three nomenclature systems, the way they were implemented, and the effects of wartime events, that can be very confusing. First, you will find a mixture of two or more nomenclatures in the same system! There was at least one Army radar, SCR-296-A, that included a Navy I.F. strip, CAOS-50AEY (see Modification Work Order 11-1505-1). Additionally, various AN nomenclatured systems contained either Army nomenclature or Navy nomenclature components. Model or component numbers can provide confusion in a variety of ways. For example, if someone offers you an "ARC-1", is he describing the AN/ARC-1 VHF transceiver or the Navy Model ARC-1 countermeasures receiver? Additionally, commercial manufacturers were fond of assigning "R-xx" or "T-xx" model numbers to their transmitters and receivers. Then we have the famous Aircraft Radio Corporation, with their ARC Type 12 and ARC Type 15, etc. systems. The Navy type numbers were sufficiently weird to preclude most confusion problems, but did you know that there are 21 identical component prefixes in the Army and AN systems? Fortunately, eleven of these (BA, BZ, GP, LC, LM, LS, ML, PH, RL, ST, and TL) are essentially the same in both systems. The rest (C, CO, CP, F, J, M, R, T, TD, and TS) have radically different meanings in the two systems, and you'd better watch out. Even in a single service model, multiple manufacturers can confuse the issue. Your BC-348-J, N, or Q was made by Wells Gardner. Others, such as the E, M, P, or S would have been made by a different manufacturer, and will have different schematics and tube lineups. The same warning applies to a number of Navy receiver models. In this case, it pays to get the manufacturer's code prefix, as well as the rest of the Navy type number. In some listings of type numbers, even the Navy left blanks in front of the type number due to the large number of contractors involved. Worse yet, the horse-trading between services over priorities at various plants led to Army and Air Corps use of Navy radio models and vice versa. As if that weren't bad enough, one look at an equipment listing for either service shows a fairly large number of commercial models in use, in addition to all the military gear. This is particularly evident in aircraft installations and in test equipment, where names like Bendix, RCA, Dumont, and General Radio keep cropping up. Even the venerable Hallicrafters S-27 did its bit as a countermeasures receiver, first for the British, and later in American "ferret" aircraft making electronic intelligence flights over enemy territory. 7. Conclusions: The Army system was relatively robust, but had several category pairs (such as I and IS) where reasonable confusion could exist as to the correct category to use. The old two- letter Navy model system was incapable of coping with wartime expansion, in terms of a great many additional models. The three-letter Navy system was no better in a few areas, notably those involving airborne systems. (A single letter limited the system to no more than 26 models.) The AN system appears to be the most robust, in terms of expansion and flexibility, and this is proved by its survival. There is one more aspect that has not been thoroughly explored. It involves dual assignments of both Army nomenclature and British Air Ministry "reference numbers" to quite a few systems. Airborne radio, radar, and IFF systems in particular carry both the Signal Corps tag and a cute little red tag with a crown and Air Ministry reference numbers. As far as I know, no one has ever come up with a cross-reference list of these numbers. If you have this type of information, I'd sure like to know about it! Now that you know the nomenclature systems, where do you find listings of the equipment? (I'll give you a hint -- they're far too lengthy to publish here.) I'd recommend the Antique Wireless Association's annual "AWA Review": Volume 6 has Fred Chesson's list of Army-nomenclature equipment, Volume 7 has Fred's list of the Navy manufacturer's codes (which the Army also used), and Volume 8 contains a pretty good list of the Navy models. The Navy type number list runs about 1600 pages, and is not for sale anywhere I've looked. Additional information on Army equipment can be found in Army TM 11-227 (a directory of radio gear), TM 11-486 (Communication Systems Engineering), and TM 11-487 (Communication Systems Equipment). SHIPS 275 (Navy Catalogue of Radio Equipment) is available from New Wireless Pioneers at (716) 681-3186. Good luck, and good hunting. If this has helped you, my work will have been worthwhile. I hope to publish an article on the technical manual numbering systems of the Army, Air Corps, Bureau of Ships, and Bureau of Aeronautics in the near future. Unfortunately, lists of BuShips publications are hard to find and I'll need help from "out there".
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