Electrical switch symbols are standardized graphical representations used in electrical diagrams to show how switches, push buttons, and control devices operate in a circuit. They are essential in IEC and ANSI schematic drawings for industrial automation and electrical engineering design.
Understanding push and switch symbols ensures design accuracy and increases maintenance effectiveness.
From pressure switch symbols to light switch symbols, they are the foundation for describing all electrical circuits.
They may be difficult to understand because there are a lot of symbols, but do not be intimidated by their complexity.
Let’s simplify that process to help you decode them.
Electrical switch symbols are defined under different international standards. The two most commonly used standards are IEC (International Electrotechnical Commission) and ANSI (American National Standards Institute).
IEC symbols are widely used in Europe and international industrial projects. They focus on functional representation and simplified schematic design.
ANSI symbols are mainly used in North America and tend to show more detailed physical structure representation.
| Feature | IEC | ANSI |
|---|---|---|
| Region | Europe and international markets | United States and North America |
| Symbol style | Simplified functional symbols | Detailed schematic symbols |
| Focus | Circuit behavior | Physical representation of components |
A normally open contact remains open in its default state. The circuit does not allow current flow until the switch is activated.
A normally closed contact remains closed in its default state. The circuit allows current flow until the switch is activated, which opens the circuit.
These two states are the foundation of most electrical switch and push button symbols.
Its sign is composed of two lines indicating the connections and with a gap between them.
There is also an extended line to one of them that connects or disconnects the circuits.
In switches, these expanded lines can be referred to as toggles or rockers.
In all configurations, you may see that these lines have circles at the ends that indicate their connection points.
In a normally open switch or button, electricity does not flow across the circuit unless activated.
Photo by: Langir
Similar to NO, but the left line touches the other with no gaps.
It could have circles at the ends too, with the extended line touching the opposing sphere, indicating that the contacts are closed in their regular state.
This indicates that electricity flows through the circuit before the switch or button is pressed.
It has two short lines that illustrate the switch contacts.
Furthermore, it is also symbolized with a gap in the circuit with a button over it, which appears as a long vertical line.
A normally open (NO) push button keeps the circuit open until pushed, which is portrayed by the vertical line bridging the gap between the two other lines.
While a normally closed (NC) push button keeps the circuit closed until it is pressed to open it.
Other key operational details to remember:
It is shown with a circular knob with an arrow pointing towards one of several connection points.
This refers to its capacity to rotate or switch between several connections or circuits.
This switch symbol is often depicted with two lines too; sometimes it may have circles at the end as contacts.
The lines represent the two terminals, which can be either closed or open.
When the line is broken, the switch’s circuit remains open.
However, it is closed when a straight line is drawn to link the two contacts.
Furthermore, it might include an “S” with a vertical line to resemble a dollar sign symbol.
A DPDT switch controls two different circuits, each with two connection options, unlike DPST.
Hence, this switch sign consists of two vertical lines as poles and four other straight lines on the other side representing the two potential connections per pole.
This shows that a DPDT switch can link one input to any of two outputs per pole.
It displays two line pairs as the switch’s double pole, indicating that it can manage two separate circuits.
In the closed state, these lines may link, with some representations showing dotted lines linking the two poles.
While in the open state, both pairs are disconnected.
These demonstrated that both circuits are either on or off simultaneously.
SPDT’s symbol is similar to SPST, except it has a Y-shaped structure, with a single “line” serving as the common terminal and the other two as traveler connections.
It could also include a tiny 3-digit number directly next to the “S“.
The digit represents how many locations you can control a light from.
Another configuration that is similar to this is the four-way switch symbol, which has a 4-digit number next to the “S.”
This switch symbol is frequently shown with a circle or a floating object linked to a line, representing the switch mechanism.
The line represents the switch mechanism, which is activated by the float’s movement.
Its function depends on its default state:
Light switch symbols share the electrical configurations’ visuals, such as SPST, SPDT, DPST, and DPDT.
Another example is the push button light switch symbol shows no differences between other push button switches.
However, there are specific configurations for light switches.
Dimmer switches, for example:
They are used only for light switches and are depicted by a little circle with a line and an arc.
The circle represents the dimmer, the line indicates the adjustment capabilities and the arch portrays voltage changes to get various brightness levels.
This switch symbol is typically represented by two lines as connecting points, one of which has an angular shape at the bottom.
The one with an angular shape is the actuator that moves to activate the switch.
Furthermore, limit switches guarantee that operations stay within set parameters to minimize damage or accidents.
So, when an object makes a physical connection with an actuator, the circuit will be either opened or closed, depending on whether it is an NO or NC switch.
It includes a switch contact with an extending line to one of them as the toggle or rocker, and a semicircle below it, which represents the pressure-sensitive actuator.
The switch’s state changes in response to applied pressure.
Pressure switches have 3 contact types:
The heat-sensing mechanism can be illustrated as a spring or curved line beneath one of the connection lines.
Similar to other symbols, it can include a circle at the end of the lines to indicate the switch contacts.
Like the float switch, it can activate or deactivate a circuit when it detects changes in temperature, depending on whether it is a NO or NC switch.
Momentary switches are active just when pressed and return to their original state when released.
Its representation is quite similar to the push button switch symbols, but it differs from its function:
Electrical switch symbols are standardized representations used in IEC and ANSI electrical diagrams. They are commonly categorized into manual switches, control switches, and industrial control switches.
Understanding these symbols improves the ability to read electrical schematics and supports accurate system design, installation, and maintenance.
If you have more questions, contact IGOTO for expert advice, and even consider getting a quote from a leading switch and socket manufacturer.
You may be creating an office at home and are fed up with wires on your desk — there is a smartphone, another smartphone, a tablet, and a laptop, and to top it all off, the lamp needs plugging in, too. Or perhaps you are a builder making a kitchen renovation and your client has […]
Suppose you need to renovate a hallway featuring two endings, with light fixtures at both ends. Or you have a living room that has four ceiling lights controlled by a pair of switches. That raises the same question: such arrangement is possible with a number of 3-way switches scattered along the way of wiring. The […]
You are at the entrance of some steps, in darkness, unable to turn on the light until after reaching the top and flipping the switch. You either have to go up the stairs in utter darkness or head back to the light switch to turn on the lights. The simple solution is to have two […]
No.6 Tuozhan Road, Leshang Pioneer Park,Yueqingwan Bay Harbor,Yueqing city,Zhejiang Province 
