A Schematic Diagram Of A Single Pole Double Throw Relay

In electronic circuits, there are many electronic symbols that are used to represent or identify a basic electronic or electrical device. They are mostly used to draw a circuit diagram and are standardized internationally by the IEEE standard (IEEE Std 315) and the British Standard (BS 3939). NO changes can be brought by the user on any electronic symbol, but the user is free to bring any changes in the architectural drawings like power source and lighting.

Electronic Symbols

The symbols for different electronic devices are shown below. Click on each link given below to view the symbols. Apart from the circuit symbols, each device is also designated a short name. Though these names are not approved as standard notations, they are commonly used by most people. These designations are also given in the list.

Wire Symbols

Electronic Component	Circuit Symbol	Description
Wire	Wire Circuit Symbol	Used to connect one component to another.
Wires Joined	Wires Joined Circuit Symbol	One device may be connected to another through wires. This is represented by drawing "blobs" on the point where they are shorted.
Unjoined Wires	Wires Not Joined Circuit Symbol	When circuits are drawn some wires may not touch others. This can only be shown by bridging them or by drawing them without blobs. But bridging is commonly practised as there will not arise any confusion.

Power Supply Symbols

Electronic Component	Circuit Symbol	Description
Cell	Cell Circuit Symbol	Used to provide a supply for a circuit.
Battery	Battery Circuit Symbol	A battery has more than a cell and is used for the same purpose. The smaller terminal is negative and the larger one is positive. Abbreviated as 'B'.
DC Supply	DC Supply Circuit Symbol	Used as a DC power supply, that is, the current will always flow in one direction.
AC Supply	AC Supply Circuit Symbol	Used as AC power supply, that is, the current will keep alternating directions.
Fuse	Fuse Circuit Symbol	Used in circuits where a probability of excessive current flows. The fuse will break the circuit if excessive current flows and saves the other devices from damage.
Transformer	Transformer Circuit Symbol	Used as an ac power supply. Consists of two coils, the primary and secondary that are linked together through an iron core. There is no physical connection between the two coils. The principle of mutual inductance is used to obtain power. Abbreviated as 'T'.
Earth/Ground	Earth Circuit Symbol	Used in electronic circuits to represent the 0 volts of the power supply. It can also be defined as the real earth , when it is applied in radio circuits and power circuits.

Resistor Symbols

Electronic Component	Circuit Symbol	Description
Resistor	Resistor Circuit Symbol	A resistor is used to restrict the amount of current flow through a device. Abbreviated as 'R'.
Rheostat	Rheostat Circuit Symbol	A rheostat is used to control the current flow with two contacts. Applicable in controlling lamp brightness, capacitor charge rate, etc.
Potentiometer	Potentiometer Circuit Symbol	A potentiometer is used to control the voltage flow and has three contacts. Have applications in changing a mechanical angle change to an electrical parameter. Abbreviated as 'POT'.
Preset	Preset Circuit Symbol	Presets are low cost variable resistors that are used to control the charge flow with the help of a screw driver. Applications where the resistance is determined only at the end of the circuit design.

Capacitor Symols

Electronic Component	Circuit Symbol	Description
Capacitor	Capacitor Circuit Symbol	Capacitor is a device that is used to store electrical energy. It consists of two metals plates that are separated by a dielectric. It is applicable as a filter, that is, to block DC signals and allow AC signals. Abbreviated with the letter 'C'.
Capacitor – Polarized	Capacitor-Polarised Circuit Symbol	Capacitor can be used in a timer circuit by adding a resistor.
Variable Capacitor	Variable Capacitor Circuit Symbol	Used to vary the capacitance by turning the knob. A type of variable capacitor is the trimmer capacitor that is small in size. The notations are all the same.

Diode Symbols

Electronic Component	Circuit Symbol	Description
Diode	Diode Circuit Symbol	A diode is used to allow electric current to flow in only one direction. Abbreviated as 'D'.
Light Emitting Diode (LED)	LED Circuit Symbol	LED is used to emit light when a current is passed through the device. It is abbreviated as LED.
Zener Diode	Zener Diode Circuit Symbol	After a breakdown voltage, the device allows current to flow in the reverse direction as well. It is abbreviated as 'Z'.
Photo Diode	Photo Diode Circuit Symbol	Photodiode works as a photo-detector and converts light into its corresponding voltage or current.
Tunnel Diode	Tunnel Diode Circuit Symbol	Tunnel Diode is known for its high-speed operation due to its application in quantum mechanical effects.
Schottky Diode	Schottky Diode Circuit Symbol	The Schottky Diode is known for its large forward voltage drop and hence has great applications in switching circuits.

Transistor Symbols

Electronic Component	Circuit Symbol	Description
NPN Transistor	Transistor NPN Circuit Symbol	This is a transistor with a layer of P-doped semiconductor fixed between two layers of N-doped semiconductors that act as the emitter and collector. Abbreviated as 'Q'.
PNP Transistor	Transistor PNP Circuit Symbol	This is a transistor with a layer of N-doped semiconductor fixed between two layers of P-doped semiconductors that act as the emitter and collector. Abbreviated as 'Q'.
Phototransistor	Phototransistor Circuit Symbol	The working of a phototransistoris similar to that of a bipolar transistor with a difference that it converts light into its corresponding current. The phototransistor can also act as a photodiode if the emitter is not connected.
Field Effect Transistor	Field Effect Transistor Circuit Symbol	Like a transistor, a FET has three terminals, the Gate, Source and Drain. The device has an electric field that controls the conductivity of a channel of one type charge carrier in a semiconductor substance.
N-Channel Junction FET	n-channel Junction Field Effect Transistor (JFET) Circuit Symbol	The Junction Field Effect Transistor (JFET) is the simplest type of FET with applications in Switching and voltage variable resistor. In an N-channel JFET an N-type silicon bar has two smaller pieces of P-type silicon material diffused on each sides of its middle part, forming P-N junctions.
P-Channel Junction FET	p-channel Junction Field Effect Transistor (FET) Circuit Symbol	P-channel JFET is similar in construction to N-channel JFET except that P-type semiconductor base is sandwiched between two N-type junctions. In this case majority carriers are holes.
Metal Oxide Semiconductor FET	Given Below	Abbreviated as MOSFET. MOSFET is a three terminal device and is controlled by a gate bias. It is known for its low capacitance and low input impedance.
Enhancement MOSFET	e-MOSFET Circuit Symbol	The enhancement MOSFET structure has no channel formed during its construction. Voltage is applied to the gate, so as to develop a channel of charge carriers so that a current results when a voltage is applied across the drain-source terminals. Abbreviated as e-MOSFET.
Depletion MOSFET	d-MOSFET Circuit Symbol	In the depletion-mode construction a channel is physically constructed and a current between drain and source is due to voltage applied across the drain-source terminals. Abbreviated as d-MOSFET.

Logic Gate Symbols

Gate	Standard Symbol	IEC Symbol	Description
AND Gate	AND GATE Symbol	AND Gate IEC Symbol	If all the inputs of an AND gate are HIGH, then the output will also be HIGH. If any one of them is LOW, the output will also be LOW.
NAND Gate	NAND Gate Symbol	NAND Gate IEC Symbol	Short form for NOT AND Gate. Of all the inputs are HIGH, the output will be LOW. If any one input is LOW, the output will be HIGH.
OR Gate	OR Gate Symbol	OR Gate IEC Symbol	If any one of the input is HIGH, the output will also be HIGH. If both inputs are LOW, the output will also be LOW.
NOR Gate	NOR Gate Symbol	NOR Gate IEC Symbol	Short form for NOT OR. If both inputs are LOW, the output will also be LOW. For other cases, the output will be HIGH.
EX-OR Gate	EX-OR Gate Symbol	EX-OR Gate IEC Symbol	Short form for Exclusive NOR. If both inputs are either in LOW state r HIGH state, the output will be LOW. If both inputs are different, the output will be HIGH.
EX-NOR Gate	EX-NOR Gate Symbol	EX-NOR Gate IEC Symbol	Short form for Exclusive NOT OR. If both the inputs are the same, the output will be HIGH. If both are different, the output will also be different.
NOT Gate	NOT Gate Symbol	NOT Gate Symbol	Also known as the inverter Gate. There is only one input for this gate. If the input is HIGH, the output will be LOW. If the input is LOW, the output will be HIGH.

Meters

Electronic Component	Circuit Symbol	Description
Voltmeter	Voltmeter Circuit Symbol	Voltmeter is used to measure the voltage at a certain point in the circuit.
Ammeter	Ammeter Circuit Symbol	An Ammeter is used to measure the current that passes through the circuit at a particular point.
Galvanometer	Galvanometer Circuit Symbol	A galvanometer is used to measure very small currents in the order of 1 milli ampere or less.
Ohmmeter	Ohmmeter Circuit Symbol	Resistance of the circuit is measured using an Ohmmeter.
Oscilloscope	Oscilloscope Circuit Symbol	An oscilloscope is used to measure the voltage and time period of signals along with their shape display.

Sensor Symbols

Electronic Component	Circuit Symbol	Description
Light Dependent Resistor (LDR)	LDR Circuit Symbol	It is abbreviated as LDR. Light Dependent Resistor is used to convert light into its corresponding resistance. Instead of directly measuring the light, it senses the heat content and converts it onto resistance.
Thermistor	Thermistor Circuit Symbol	Instead of directly measuring the light, a thermistor senses the heat content and converts it into resistance. Abbreviated as 'TH'.

Switch Symbols

Electronic Component	Circuit Symbol	Description
Push Switch	Push Switch Circuit Symbol	This is an ordinary switch that passes current only upon pressing.
Push to Break Switch	Push to Break Switch Circuit Symbol	The push to break switch is usually kept in the ON state (closed). It turns to OFF state (open) only when the switch is pressed.
Singe Pole Single Throw Switch	On Off Switch (SPST) Circuit Symbol	Also known as the ON/OFF switch. This switch allows the flow of current only when it is kept ON. Abbreviated as SPST.
Single Pole Double Throw Switch	2-Way Switch (SPDT) Circuit Symbol	Also known as the 2-way switch. It can be also called as an ON/OFF/ON switch as it has an OFF position in the center. The switch causes the flow of current in two directions, depending on its position. It can be abbreviated as SPDT.
Double Pole Single Throw Switch	Dual On-Off Switch (DPST) Circuit Symbol	Abbreviated as DPST. Can also be called as a dual ON-OFF switch. This is used to isolate between the live and neutral connections in the main electrical line.
Double Pole Double Throw Switch	DPDT Circuit Symbol	Abbreviated as DPDT. The switch uses a central OFF position and is applied as reversing switch for motors.
Relay	Relay Circuit Symbol	Relay is abbreviated as 'RY'. This device can easily switch a 230 Volt AC mains circuit. It has three switching stages called Normally Open (NO). Normally Closed (NC), and Common (COM).

Audio and Radio Device Symbols

Electronic Component	Circuit Symbol	Description
Microphone	Microphone Circuit Symbol	This device is used for converting sound to its corresponding electrical energy. Abbreviated as 'MIC'.
Earphone	Earphone Circuit Symbol	Does the reverse process of microphone and converts electrical energy into sound.
Loudspeaker	Loudspeaker Circuit Symbol	Does the same operation as an earphone, but converts an amplified version of the electrical energy into its corresponding sound.
Piezo-Transducer	PiezoTransducer Circuit Symbol	It is a transducer that converts electrical energy into sound.
Amplifier	Amplifier Circuit Symbol	Used to amplify a signal. It is mainly used to represent a whole circuit rather than just one component.
Aerial	Aerial Circuit Symbol	This device is used to transmit/receive signals. Abbreviated as 'AE'.

Output Devices

Electronic Component	Circuit Symbol	Description
Lighting Lamp	Lamp Circuit Symbol	This is used to provide light for the output.
Indicator Lamp	Lamp Indiator Circuit Symbol	Used to convert electrical energy into light. The best example is the warning light on a car dashboard.
Heater	Heater Circuit Symbol	This transducer is used to change electrical energy into heat.
Inductor	Inductor Circuit Symbol	Inductor is used to produce a magnetic field when a certain current is passed through a coil of wire. The wire is coiled on a soft iron core. Have applications in motors, and tank circuits. Abbreviated as 'L'.
Motor	Motor Circuit Symbol	This device is used to convert electrical energy into mechanical energy. Can be used as a generator as well. Abbreviated as 'M'.
Bell	Bell Circuit Symbol	Used to produce a sound as the output, according to the electrical energy produced as the input.
Buzzer	Buzzer Circuit Symbol	It is used to produce an output sound corresponding to the electrical energy in the input.