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Electrical & Electronic Symbols

Electrical & Electronic Symbols



Component name


Wire Symbols

Electrical Wire

Conductor of electrical current


Connected Wires

Connected crossing


Non Connected Wires

Wires that cross & are not connected

Switch Symbols and Relay Symbols

SPST Switch

Disconnects current when open


SPDT Switch

Selects between two connections


Pushbutton Switch (N.O)

Momentary switch - Normally Open


Pushbutton Switch (N.C)

Momentary switch - Normally Closed


DIP Switch

DIP switch is used for on-board configuration


SPST Relay

Relay open / close connection by an electromagnet


SPDT Relay



Close connection by jumper insertion on pins.


Solder Bridge

Solder to close connection

Ground Symbols

Earth Ground

Used for zero potential reference and electrical shock protection.


Chassis Ground

Ground connected to the chassis.

Resistor Symbols

Resistor (IEEE)

Resistor reduces the current flow.


Resistor (IEC)


Potentiometer (IEEE)

Adjustable resistor - has 3 terminals.


Potentiometer (IEC)


Variable Resistor / Rheostat (IEEE)

Adjustable resistor - has 2 terminals.


Variable Resistor / Rheostat (IEC)


Trimmer Resistor

Pre-set resistor



Thermal resistor - change resistance when temperature changes


Photo Resistor / Light dependent resistor (LDR)

Photo Resistor - change resistance with light intensity change

Capacitor Symbols


Capacitor is used to store electric charge. It acts as short circuit with AC and open circuit with DC.




Polarized Capacitor

Electrolytic capacitor


Polarized Capacitor

Electrolytic capacitor


Variable Capacitor

Adjustable capacitance

Inductor / Coil Symbols


Coil / solenoid that generates magnetic field


Iron Core Inductor

Includes iron


Variable Inductor

 Moving the core farther into the coil increases the permeability, increasing the magnetic field and the inductance.

Power Supply Symbols

Voltage Source

Generates constant voltage


Current Source

Generates constant current.


AC Voltage Source

AC voltage source



Electrical voltage is generated by mechanical rotation of the generator


Battery Cell

Generates constant voltage



Generates constant voltage


Controlled Voltage Source

Generates voltage as a function of voltage or current of other circuit element.


Controlled Current Source

Generates current as a function of voltage or current of other circuit element.

Meter Symbols


Measures voltage. Has very high resistance. Connected in parallel.



Measures electric current. Has near zero resistance. Connected serially.



Measures resistance



Measures electric power

Lamp / Light Bulb Symbols

Lamp / light bulb

Generates light when current flows through


Lamp / light bulb


Lamp / light bulb

Diode / LED Symbols


Diode allows current flow in one direction only (left to right).


Zener Diode

Allows current flow in one direction, but also can flow in the reverse direction when above breakdown voltage


Schottky Diode

Schottky diode is a diode with low voltage drop


Varactor / Varicap Diode

Variable capacitance diode


Tunnel Diode

 A type of semiconductor that is capable of very fast operation, well into the microwave frequency region, made possible by the use of the quantum mechanical effect called tunnelling.


Light Emitting Diode (LED)

LED emits light when current flows through



Photodiode allows current flow when exposed to light

Transistor Symbols

NPN Bipolar Transistor

Allows current flow when high potential at base (middle)


PNP Bipolar Transistor

Allows current flow when low potential at base (middle)


Darlington Transistor

Made from 2 bipolar transistors. Has total gain of the product of each gain.


JFET-N Transistor

N-channel field effect transistor


JFET-P Transistor

P-channel field effect transistor


NMOS Transistor

N-channel MOSFET transistor


PMOS Transistor

P-channel MOSFET transistor

Misc. Symbols


Electric motor



Change AC voltage from high to low or low to high.


Electric bell

Rings when activated



Produce buzzing sound



The fuse disconnects when current above threshold. Used to protect circuit from high currents.



Contains several wires. Usually for data / address.






Optocoupler / Opto-isolator

Optocoupler isolates connection to other board



Converts electrical signal to sound waves



Converts sound waves to electrical signal


Operational Amplifier

Amplify input signal


Schmitt Trigger

Operates with hysteresis to reduce noise.


Analog-to-digital converter (ADC)

Converts analog signal to digital numbers


Digital-to-Analog converter (DAC)

Converts digital numbers to analog signal


Crystal Oscillator

Used to generate precise frequency clock signal

Antenna Symbols

Antenna / aerial

Transmits & receives radio waves


Antenna / aerial


Dipole Antenna

Two wires simple antenna

Logic Gates Symbols

NOT Gate (Inverter)

Outputs 1 when input is 0


AND Gate

Outputs 1 when both inputs are 1.



Outputs 0 when both inputs are 1. (NOT + AND)


OR Gate

Outputs 1 when any input is 1.


NOR Gate

Outputs 0 when any input is 1. (NOT + OR)


XOR Gate

Outputs 1 when inputs are different. (Exclusive OR)


D Flip-Flop

Stores one bit of data


Multiplexer / Mux 2 to 1

Connects the output to selected input line.


Multiplexer / Mux 4 to 1


Demultiplexer / Demux 1 to 4

Connects selected output to the input line.



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