An electronic symbol is a pictogram used to represent various electrical and electronic devices (such as wires, batteries, resistors, and transistors) in a schematic diagram of an electrical or electronic circuit. These symbols can (because of remaining traditions) vary from country to country, but are today to a large extent internationally standardized. Some symbols represent components which ceased to be used routinely as newer technologies were introduced (such as vacuum tubes).
Standards for symbols 
There are several national and international standards for graphical symbols in circuit diagrams, in particular:
- IEC 60617 (also known as British Standard BS 3939)
- ANSI standard Y32 (also known as IEEE Std 315)
- Australian Standard AS 1102
Different symbols may be used depending on the discipline using the drawing. For example, lighting and power symbols used as part of architectural drawings may be different from symbols for devices used in electronics. National and local variations to international standards also exist.
Reference designations 
A reference designator unambiguously identifies a component in an electrical schematic (circuit diagram) or on a printed circuit board (PCB). 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.
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.
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.
Especially valuable is the method of referencing and annotating cables plus their connectors within and outside assemblies. Examples:
- 1A1A44J5 - Unit 1, Assembly 1, Sub-Assembly 44, Jack 5 (J5 is a connector on a box referenced as A44)
- 1A1A45J333 - Unit 1, Assembly 1, Sub-Assembly 45, Jack 333 (J333 is a connector on a box referenced as A45)
A cable connecting these two might be:
- 1A1W35 - In the assembly A1 is a cable called W35.
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.
The construction of reference designators is covered by IEEE 200-1975/ANSI Y32.16-1975 (replaced by ASME Y14.44-2008) and IEEE-315-1975. The table below lists designators commonly used, and does not comply with the standard.
|D||Diode (including Zeners, thyristors and LEDs)|
|FB or FEB||Ferrite bead|
|J||Jack connector (often, but not always, female)|
|LS||Loudspeaker or buzzer|
|MP||Mechanical part (including screws and fasteners)|
|P||Plug connector (often, but not always, male)|
|Q||Transistor (all types)|
|S||Switch (all types, including push-buttons)|
|VR||Variable resistor (potentiometer or rheostat)|
|X||Transducer not matching any other category|
|Y||Crystal or oscillator|
Component name abbreviations widely used in industry:
Gallery of common electronic symbols 
Symbols shown are typical examples, not a complete list.
Vacuum tubes 
See also 
- Standard Reference Designations for Electrical and Electronics Parts and Equipments: IEEE 200-1975 (Reaffirmed 1988): Section 184.108.40.206 (2). IEEE and ANSI, New York, NY. 1975.
- Reference Designations for Electrical and Electronics Parts and Equipment: ASME Y14.44-2008 (Replaced IEEE 200-1975). ASME, Fairfield, NJ. 2008.
- Graphic Symbols for Electrical and Electronics Diagrams (Including Reference Designation Letters): IEEE-315-1975 (Reaffirmed 1993): Section 22. IEEE and ANSI, New York, NY. 1993.
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