Emergency buttonhole, features and applications!

The buttonholes are useful and necessary components in many industrial machines and especially in electrical controls! There are several models of pushbuttons available on the market, each with a different operating system, enabling various applications. Due to the huge number of buttonholes that exist, the Electric World decided to help you, we will show you some types of buttonholes and mainly talk about the emergency buttonholes and the importance of each one.

Buttonholes: Color identification

There is a standard that specifies the buttonhole colors according to its application, so that any professional can identify the working flow of a production line or machine just by observing the colors of the buttons. The standard response for this identification is the NR 26 standard.

It aims to fix the colors that should be used in the workplace to prevent accidents, identifying safety equipment, delimiting areas, identifying the pipes used in industries to conduct liquids, gases and warning against risks. Below are the color specifications for signaling in buttonholes according to NR 26:

  • Green or Black: Start, start and start.
  • Red: Stop, turn off, emergency button.
  • Yellow: Reverse the direction, cancel the operation, cancel the dangerous condition.
  • Blue: Any function other than the previous ones.
  • White: Any function other than the previous ones.

Button types: Mushroom button or emergency button:

The emergency button, as the name implies, is used to turn off the control in case of any abnormality, for example, when an accident occurs. The emergency button needs to contain some important characteristics and one of them besides its color is to be a button of easy access, in a way that anyone can activate and with any part of the body.

Types of emergency buttonholes.


When pressed, the button is retained in its final position and to return to the initial position it is necessary to turn the emergency button clockwise, promoting its unlocking.

The emergency button has retention and is activated by pressing on its structure, returning to its normal state only when the button is turned. This maneuver makes the emergency button much safer because once pressed, the button will not return to its initial position by mistake or accidentally.

It is important to highlight that the contacts of an emergency button are normally NC contacts (Normally Closed), used to disconnect the circuit, being ideal to disconnect the seal contact.

Types of buttonholes: Buttonhole with retention or selector switch

The pushbuttons or retention keys generally have two or three positions, which can be the on and off positions, providing some advantages, for example, having only two buttons on one button and occupying less space on the control panel.

Not everything is perfect, because, despite the advantages, the use of this component also has some disadvantages, one of which is that if the power is exhausted and the circuit is in operation it will remain switched in the on position, so when the power returns the circuit will connect automatically.

This problem also occurs if a protection relay acts, because when the fault is resolved, the circuit returns to its normal operation, with the risk of accidents involving workers involved in the controlled system.

Button types: Push-button or non-retention button

The push-button or non-hold button is normally used in the control circuit in conjunction with a seal contact. If the pushbutton is not used together with a seal contact, its operation will be temporary, that is, the contact switches only while the button is pressed.

We use the button without retention for safety, because its advantage is precisely to solve the problem of the button with retention. When there is a power outage, even with the seal contact, circuit operation is interrupted, that is, when a fault occurs and the circuit is switched off, it is restarted only if the button is pressed again.

Here we always put safety first, so we have several contents related to electrical safety. Below is a video from the Mundo da Elétrica channel, in which an intelligent emergency buttonhole is presented, explaining its operation and characteristics.