Reference designator

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A reference designator unambiguously identifies a component within an electrical schematic or on a printed circuit board. The reference designator usually consists of one or two letters followed by a number, e.g. R13, C1002. The number is sometimes followed by a letter, indicating that components are grouped or matched with each other, e.g. R17A, R17B. IEEE 315 contains a list of Class Designation Letters to use for electrical and electronic assemblies. For example, the letter R is a reference prefix for the resistors of an assembly, C for capacitors, K for relays.

Electronic component basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields

An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not to be confused with electrical elements, which are conceptual abstractions representing idealized electronic components.

Circuit diagram graphical representation of an electrical circuit

A circuit diagram is a graphical representation of an electrical circuit. A pictorial circuit diagram uses simple images of components, while a schematic diagram shows the components and interconnections of the circuit using standardized symbolic representations. The presentation of the interconnections between circuit components in the schematic diagram does not necessarily correspond to the physical arrangements in the finished device.

Printed circuit board board to support and connect electronic components

A printed circuit board (PCB) mechanically supports and electrically connects electronic components or electrical components using conductive tracks, pads and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Components are generally soldered onto the PCB to both electrically connect and mechanically fasten them to it.



IEEE 200-1975 or "Standard Reference Designations for Electrical and Electronics Parts and Equipments" is a standard that was used to define referencing naming systems for collections of electronic equipment. IEEE 200 was ratified in 1975. The IEEE renewed the standard in the 1990s, but withdrew it from active support shortly thereafter. This document also has an ANSI document number, ANSI Y32.16-1975.

This standard codified information from, among other sources, a United States military standard MIL-STD-16 which dates back to at least the 1950s in American industry.

To replace IEEE 200-1975, ASME, a standards body for mechanical engineers, initiated the new standard ASME Y14.44-2008. This standard, along with IEEE 315-1975, provide the electrical designer with guidance on how to properly reference and annotate everything from a single circuit board to a collection of complete enclosures.

ASME professional association

The American Society of Mechanical Engineers (ASME) is an American professional association that, in its own words, "promotes the art, science, and practice of multidisciplinary engineering and allied sciences around the globe" via "continuing education, training and professional development, codes and standards, research, conferences and publications, government relations, and other forms of outreach." ASME is thus an engineering society, a standards organization, a research and development organization, an advocacy organization, a provider of training and education, and a nonprofit organization. Founded as an engineering society focused on mechanical engineering in North America, ASME is today multidisciplinary and global.


ASME Y14.44-2008 [1] and IEEE 315-1975 [2] define how to reference and annotate components of electronic devices.

It breaks down a system into units, and then any number of sub-assemblies. The unit is the highest level of demarcation in a system and is always a numeral. Subsequent demarcation are called assemblies and always have the Class Letter "A" as a prefix following by a sequential number starting with 1. Any number of sub-assemblies may be defined until finally reaching the component. Note that IEEE-315-1975 [2] defines separate class designation letters for separable assemblies (class designation 'A') and inseparable assemblies (class designation 'U'). Inseparable assembliesi.e., "items which are ordinarily replaced as a single item of supply" [2] are typically treated as components in this referencing scheme.


Especially valuable is the method of referencing and annotating cables plus their connectors within and outside assemblies. Examples:

A cable connecting these two might be:

Connectors on this cable would be designated:

ASME Y14.44-2008 continues the convention of Plug P and Jack J when assigning references for electrical connectors in assemblies where a J (or jack) is the more fixed and P (or plug) is the less fixed of a connector pair, without regard to the gender of the connector contacts.

Electrical connector electro-mechanical device

An electrical connector is an electro-mechanical device used to join electrical terminations and create an electrical circuit. Electrical connectors consist of plugs (male-ended) and jacks (female-ended). The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or devices. An adapter can be used to effectively bring together dissimilar connectors.

Gender of connectors and fasteners designation differentiating two dissimilar connectors which together form a physical connexion -- Used to describe connexions for spacecraft docking, electronics, plumbing, etc.

In electrical and mechanical trades and manufacturing, each half of a pair of mating connectors or fasteners is conventionally assigned the designation male or female. The "female" connector is generally a receptacle that receives and holds the "male" connector. On occasion, the terms "male" and "female" are respectively referred to as the A and B ends, though the names of some standards conflict with this as they contain the letters A or B within the name; unambiguous, though rare, terms include plug and socket or jack.

The construction of reference designators is covered by IEEE 200-1975/ANSI Y32.16-1975 [3] (replaced by ASME Y14.44-2008 [1] ) and IEEE-315-1975. [2] The table below lists designators commonly used, and does not necessarily comply with the standard.

DesignatorComponent type
ASeparable assembly or sub-assembly (e.g. printed circuit assembly)
AT Attenuator or isolator
BR Bridge rectifier
BT Battery
C Capacitor
CN Capacitor network
D Diode (including LED, TVS, thyristor, Zener)
DL Delay line
DS Display
F Fuse
FB Ferrite bead
FD Fiducial
FL Filter
G Generator or oscillator
GNGeneral network
H Hardware, e.g., screws, nuts, washers
HY Circulator or directional coupler
J Jack (least-movable connector of a connector pair) | Jack connector (connector may have "male" pin contacts and/or "female" socket contacts)
JP Jumper (Link)
K Relay or contactor
L Inductor or coil or ferrite bead
LS Loudspeaker or buzzer
M Motor
MK Microphone
MPMechanical part (including screws and fasteners)
P Plug (most-movable connector of a connector pair) | Plug connector (connector may have "male" pin contacts and/or "female" socket contacts)
PS Power supply
Q Transistor (all types)
R Resistor
RN Resistor network
RT Thermistor
RV Varistor / Variable resistor
S Switch (all types, including push-buttons)
T Transformer
TC Thermocouple
TP Test point
TUN Tuner
U Integrated circuit (IC)
V Vacuum tube
VR Voltage regulator (voltage reference) / Variable resistor (potentiometer or rheostat)
XSocket connector for another item not P or J, paired with the letter symbol for that item (XV for vacuum tube socket, XF for fuse holder, XA for printed circuit assembly connector, XU for integrated circuit connector, XDS for light socket, etc.)
XTAL Crystal
Y Crystal or oscillator
Z Zener diode

Other component name abbreviations used in industry

See also

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  1. 1 2 Reference Designations for Electrical and Electronics Parts and Equipment: ASME Y14.44-2008 (Replaced IEEE 200-1975). ASME, Fairfield, NJ. 2008.
  2. 1 2 3 4 IEEE (1975), "22. Class Designation Letters", IEEE Std 315-1975: Graphic Symbols for Electrical and Electronics Diagrams (Including Reference Designation Letters) (Reaffirmed 1993), IEEE and ANSI, New York, NY
  3. Standard Reference Designations for Electrical and Electronics Parts and Equipments: IEEE 200-1975 (Reaffirmed 1988): Section (2). IEEE and ANSI, New York, NY. 1975.