Push Button Symbol
Definition: The Push Button symbol represents a momentary-action switch with two terminals (A and B) that closes its contacts only while pressed and returns to its open (rest) state when released, depicted in circuit diagrams per IEC 60617-07 and ANSI Y32.2/IEEE 315 as two contact circles connected by a dashed line with an operating button rectangle above the actuator, used to initiate momentary electrical signals in control, electronic, and consumer circuits.
Also known as: momentary switch, tactile switch, pushbutton, normally-open button, PBS, momentary push-button switch.
What the Push Button symbol means
The Push Button symbol in a circuit diagram denotes a manually operated momentary-contact switch that completes or breaks a circuit only for the duration of the button press. Unlike a toggle or latching switch that remains in its new state after actuation, a push button automatically returns to its rest state (open or closed) when the operator releases the button.
Push buttons appear throughout control circuits, consumer electronics, industrial control panels, and embedded systems. The normally-open (NO) variant — the most common — keeps the circuit open at rest and closes it only when pressed, making it suitable for momentary start signals, momentary enable inputs, and user interface buttons. The push button symbol communicates to the reader that the circuit expects a brief, transient input rather than a sustained switched state.
How to identify the Push Button symbol
The push button symbol in the NO (normally open) configuration shows two filled circles representing the contact terminals (A on the left, B on the right) connected by a short horizontal dashed line indicating the gap between the open contacts. A vertical line rises from the centre of the contact pair to a small rectangle at the top, representing the actuator button body. In ANSI/IEEE 315 style, the contact blade is a diagonal line rising from the lower contact to near the upper contact with a gap; an arrow or rectangle above the blade indicates push actuation. IEC 60617-07 uses a similar diagonal contact line with a button actuator symbol.
Function in a circuit
A push button contains a spring-loaded contact mechanism: pressing the button compresses the spring and forces the moving contact against the fixed contact, completing the circuit between terminals A and B. Releasing the button allows the spring to retract the moving contact, breaking the circuit. In momentary normally-closed (NC) push buttons, the contacts are closed at rest and open when pressed. Push buttons are available with LED indicators, key-lock mechanisms, mushroom heads (emergency stop), flush or protected heads, and illuminated rings for visual feedback.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617-07 (Switching devices) defines the push button contact symbol as a make-contact (NO) or break-contact (NC) symbol with a manually-operated non-locking actuator indicator. IEC 60947-5-1 defines the construction and performance requirements for push buttons in low-voltage control circuits. |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2 / IEEE 315-1975 defines the push button symbol as a switch contact with a push-type actuator. The contact is shown as a diagonal line with two terminal circles; the push actuator is indicated by a rectangular symbol above the contact blade. |
| Key difference | IEC 60617-07 uses a simplified contact symbol with an actuator mark for the push button. ANSI Y32.2 / IEEE 315 shows a similar diagonal-blade contact with a rectangle or arrow for the push actuator. Both standards produce visually similar symbols; IEC diagrams may show the actuator annotation differently from ANSI diagrams but both are immediately recognisable as push buttons. |
Terminals / pins
| Pin | Name |
|---|---|
| a | A |
| b | B |
Typical values
Contact rating: 0.1–10 A at 12–250 V AC/DC for panel-mount types. Tactile switch: 50–500 mA at 5–12 V DC for PCB-mount. Actuation force: 1–5 N. Mechanical life: 1,000,000 cycles (tactile); 1,000,000–10,000,000 cycles (panel push button). Contact resistance: <30 mΩ. Bounce time: 1–10 ms (requires software debouncing for microcontroller inputs).
Where the Push Button symbol is used
- Industrial motor control circuits: momentary START (NO) and STOP (NC) push buttons for motor starter control
- Emergency stop (E-stop) circuits: large mushroom-head NC push buttons per IEC 60947-5-5 / ISO 13850
- Microcontroller and Arduino/Raspberry Pi GPIO inputs for user interaction
- Consumer electronics: power, play/pause, volume, and menu navigation buttons
- Elevator and lift call buttons: momentary signals to floor-call and cabin-destination controllers
- Doorbell circuits: momentary contact triggering a chime or smart doorbell notification
Example
In a three-phase motor starter circuit, the push button symbol for START (NO, green) connects in parallel with the contactor's sealing contact (auxiliary NO) and in series with the STOP button (NC, red) and contactor coil. Pressing START closes the circuit for the coil to energise; the sealing contact then holds the circuit closed after the button is released, maintaining the run state until STOP is pressed.
Key facts
- The Push Button symbol in IEC 60617-07 and ANSI Y32.2 / IEEE 315-1975 represents a momentary-action switch with terminals A and B that closes (NO) or opens (NC) only while pressed and returns to its rest state when released.
- Normally-open (NO) push buttons keep the circuit open at rest and close when pressed; normally-closed (NC) push buttons keep the circuit closed at rest and open when pressed.
- The push button has two terminals: A and B (the switch contacts). On PCB tactile switches, these may be labelled pin 1/2 and pin 3/4 (each pair is internally connected) for a through-hole 4-pin package.
- Emergency stop push buttons follow IEC 60947-5-5 and ISO 13850: they must be mushroom-head, red on yellow background, direct-opening action (NC contacts that cannot weld closed), and latch in the pressed position until deliberately reset.
- Push button contact bounce (1–10 ms of rapid on/off transitions at actuation) must be handled in microcontroller firmware by software debouncing or by hardware RC debounce circuits to prevent multiple-edge triggering.
- The reference designator for a push button in schematics is SW (switch) or PB (push button) followed by a number, e.g. SW1 or PB3, per IEEE 315-1975.
- Illuminated push buttons incorporate an LED or lamp behind a translucent cap to provide status indication; they use an additional supply connection beyond the two contact terminals.
Diagrams that use this symbol
- electrical connection diagram
- electrical circuit diagram
- electric circuit diagram
- electrical wiring diagram
- electrical diagram
- wiring drawing
- electrical schematic
- plc diagram
Frequently asked questions
What does the push button symbol look like in a circuit diagram?
The normally-open push button symbol shows two contact circles (terminals A and B) connected by a dashed line indicating an open gap, with a vertical line rising to a small rectangle representing the button actuator above the contacts. When the button is pressed, the gap closes and the circuit is completed.
What does the push button symbol mean?
The push button symbol indicates a momentary switch that connects or disconnects the circuit only while it is being physically pressed. Releasing the button automatically returns the contacts to their rest state — open for NO types, closed for NC types.
What is the difference between a normally open and normally closed push button?
A normally open (NO) push button has open contacts at rest (circuit broken) and closes the circuit when pressed. A normally closed (NC) push button has closed contacts at rest (circuit completed) and opens the circuit when pressed. NO is used for START functions; NC is used for STOP and emergency stop functions.
What standard defines the push button symbol?
IEC 60617-07 defines the push button switch symbol as a manually operated non-locking contact device. ANSI Y32.2 / IEEE 315-1975 provides the equivalent North American symbol. IEC 60947-5-1 governs the construction and performance of push button devices in low-voltage control circuits.
What is the designator letter for a push button?
Push buttons are designated SW (switch) or PB (push button) in schematics, followed by a sequential number such as SW1 or PB2. In motor control diagrams, START buttons are often labelled PB-START or PB1, and STOP buttons PB-STOP or PB2.
What are the pins on a push button symbol?
The push button symbol shows two terminals: A and B (the switch contacts). Physical tactile switches for PCBs typically have four pins — pins 1 and 2 are internally connected, pins 3 and 4 are internally connected, with the two pairs bridged when the button is pressed.
Why does a push button cause problems with microcontrollers?
Push buttons produce contact bounce — rapid on/off transitions of 1–10 ms when the contacts first make or break — because the spring contacts physically bounce before settling. A microcontroller reading the GPIO at high speed sees multiple false edges. This is handled by software debouncing (waiting 10–20 ms after the first edge) or a hardware RC low-pass filter with a Schmitt trigger at the input.
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