Volume 1 of 2
15 December 1965
MODIFICATION LETTERS (cont' d)
Set modification letters will be assigned for each modification not affecting interchangeability of the sets or equipment
as a whole, except that in some special cases they will be assigned to indicate functional interchangeability and not
necessarily complete electrical and mechanical interchangeability. Modification letters will only be assigned if the
frequency coverage of the unmodified equipment is maintained.
The suffix letters X, Y, and Z will be used only to designate a set or equipment modified by changing the power input
voltage, phase or frequency. X will indicate the first change, Y the second, Z the third, XX the fourth etc., and these
letters will be in addition to other modification letters applicable. (For examples see MIL-STD-196B).
Experimental Sets. In order to identify a set or equipment of an experimental nature with the development organization
concerned, the following indicators will be used with the parenthesis:
RTD/ASD, Wright-Patterson Air Force Base, Ohio.
Naval Research Laboratory, Washington, D.C.
U.S. Army Signal Engineering Laboratories, The Hexagon, Fort Monmouth, N.J. (inactivated, use XE).
Electronic Systems Division, Laurence G. Hanscom Field, Bedford, Massachusetts.
U.S. Army Electronics Laboratories, Fort Monmouth, N.J.
Frankford Arsenal, Philadelphia, Pa.
U.S.N. Electronics Laboratory, San Diego, California.
Aerial Reconnaissance Laboratory, Wright-Patterson Air Force Base, Ohio.
Det 4, RTD, Eglin Air Force Base, Florida.
Naval Air Development Center, Johnsville, Pa.
Flight Control Laboratory, Wright-Patterson Air Force Base, Ohio
U.S. Army Signal Electronics Research Unit, Mountain View, Calif.
U.S. Army Signal Engineering Laboratories, The Hexagon, Fort Monmouth, N.J. (inactivated, use XE)
Department of the Navy, Washington, D.C.
U.S. Army Missile Command, Redstone Arsenal, Alabama.
Canadian Department of National Defense, Ottawa, Canada.
Aeronautical Accessories Laboratory, Wright-Patterson Air Force Base, Ohio.
National Security Agency, Fort George G. Meade, Maryland.
Electronic Components Laboratory, Wright-Patterson Air Force Base, Ohio.
U.S. Army Security Agency, Arlington Hall Station, Arlington, Va.
U.S. No Underwater Sound Laboratory, Fort Trumbell, New London, Conn.
Air Force Weapons Laboratory, Kirtland Air Force Base, New Mexico.
Rome Air Development Center, Rome, New York
Weapons Guidance Laboratory, Wright-Patterson Air Force Base, Ohio.
U.S.N. Bureau of Naval Weapons Activities.
Air Force Ballistic Systems Division, Norton Air Force Base, Calif.
U.S. Army Electronics Research and Development Activity, Fort Huachuca, Arizona.
Naval Avionics Facility, Indianapolis, Ind.
U.S. Army Electronics Command, Proc and Prod Dir., Fort Monmouth, N.J.
Air Force Missile Test Center, Patrick Air Force Base, Florida.
U.S. Army Signal Air Defense Engineering Agency, Fort George G. Meade, Maryland.
U.S. Army Limited War Laboratory, Aberdeen Proving Ground, Maryland.
U.S. Army, Project Michigan, Ypsilanti, Michigan.
NOTE: *Not for Air Force use except for assigning additional developmental designations to
previously type designated items. Use XA for all new equipments.