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If you build an electronic circuit in London, an engineer in Tokyo or Berlin should be able to read your schematic without speaking a word of your language.
To make this possible, international engineering bodies created BS EN 60617, a standardized graphical language for electronic schematics.
A passive component is any electronic part that cannot amplify signals or produce energy on its own, such as resistors and capacitors.
How do we represent components that resist electric current using this standard?
The Resistor Family
Under BS EN 60617, a fixed resistor is always drawn as an empty rectangle with connection leads extending from opposite ends.
To show adjustability, a variable resistor adds a diagonal arrow through the rectangle, while a potentiometer uses a third terminal with an arrow touching the side to represent a movable wiper.
๐A visual interactive guide displaying the three fundamental resistor symbols in BS EN 60617 standard. Card 1: Fixed Resistor (clear black rectangular box with two axial wire leads). Card 2: Variable Resistor / Rheostat (same rectangle with a 45-degree arrow slicing through the center, showing two terminals). Card 3: Potentiometer (same rectangle with two end terminals and a third lead ending in an arrow pointing directly onto the side of the rectangle). Clean layout with labels, terminal callouts, and crisp vector-like styling on a clean card background.
What happens when resistance needs to change automatically based on the environment instead of a manual knob?
Environmental Sensors
A thermistor is a temperature-sensitive resistor drawn with a characteristic 'hockey stick' line passing through the rectangular body, accompanied by โtโ (for negative temperature coefficient) or +tโ.
A light-dependent resistor (LDR) uses the base resistor rectangle with two parallel diagonal arrows pointing directly inward to signify incoming illumination.
๐Comparison diagram showing environmental sensor symbols side by side. Left: Thermistor (BS EN rectangle with a diagonal line through it that has a small horizontal foot at the bottom-left, labeled -tยฐ NTC with an annotation pointing to the hockey stick qualifier). Right: LDR (BS EN rectangle with two parallel arrows pointing inwards towards the top-left corner, labeled Light Dependent Resistor). Highlight the key modifier features in vivid blue with helpful pointer tags.