All types of resistors have their own resistor symbols which are used when a circuit diagram is drawn. This page will explain the different standards which are used for resistor symbols and display the most common symbols. Standards for resistor symbols Several standards exist, which describe how the different components should be displayed. In the past a lot of countries or even industries used their own standards, which can be confusing. Nowadays the IEC 60617 standard is international standard for these electronic symbols. However the local standards are still used from time to time. In general, the ANSI standard is still common in the United States. Some examples of standards which describe resistor symbols: IEC 60617 (International) ANSI Y32 / IEEE 315 (US) – old DIN 40900 (Germany) – old AS 1102 (Australia) – old Sometimes the symbol for a particular device is different when it is used in another field of application. Other symbols are used in electronics then for example in architecture and buildings. On top of this, many local deviations from the international standards exist. The following table shows the most common resistor symbols for electronics design. Schematic symbols Type Abbreviation IEC (International) ANSI (US) Fixed resistor R Heating resistor Variable resistors VR Potentiometer Trimming potentiometer Rheostat Preset resistor Dependent resistors Photo resistor orLight dependent resistor LDR Varistor or Voltage dependent resistor VDRRVMOV NTC thermistor NTCRT PTC thermistor PTCRT Magneto resistor orMagnetic dependent resistor MDR Read more in the Resistor Guide E-Book.