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 (such as those of vacuum tubes) became virtually extinct with the development of new technologies.
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There are several national and international standards for graphical symbols in circuit diagrams, in particular:
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.
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 standard also has an ANSI document number ANSI Y32.16-1975. They are the same document.
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, a standards body for Mechanical Engineers, ASME, 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 simple circuit board to a complete enclosure all the way to a collection of these assemblies.
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:
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 connectors in electrical 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[1] (replaced by ASME Y14.44-2008[2]) and IEEE-315-1975[3]. The table below lists designators commonly used, and does not comply with the standard.
| Designator | Component Type |
|---|---|
| AT | Attenuator |
| BR | Bridge rectifier |
| BT | Battery |
| C | Capacitor |
| CN | Capacitor network |
| D | Diode (including Zeners, thyristors and LEDs) |
| DL | Delay line |
| DS | Display |
| F | Fuse |
| FB or FEB | Ferrite bead |
| FD | Fiducial |
| J | Jack connector (often, but not always, female) |
| JP | Link (Jumper) |
| K | Relay |
| L | Inductor |
| LS | Loudspeaker or buzzer |
| M | Motor |
| MK | Microphone |
| MP | Mechanical part (including screws and fasteners) |
| P | Plug connector (often, but not always, male) |
| PS | Power supply |
| Q | Transistor (all types) |
| R | Resistor |
| RN | Resistor network |
| RT | Thermistor |
| RV | Varistor |
| S | Switch (all types, including push-buttons) |
| T | Transformer |
| TC | Thermocouple |
| TUN | Tuner |
| TP | Test point |
| U | Integrated circuit |
| V | Vacuum tube |
| VR | Variable resistor (potentiometer or rheostat) |
| X | Transducer not matching any other category |
| Y | Crystal or oscillator |
| Z | Zener diode |
Component name abbreviations widely used in industry:
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