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What is a Reed Switch and How Does it Work?

How a reed switch works with a permanent magnet positioned parallel to the switch and moving perpendicular over the center of the switch.

“What is a Reed Switch and How Does it Work – A reed switch is an electromechanical switching device that contains two ferromagnetic blades in a hermetically sealed glass envelope, so these components can exist or be used in almost any environment.”

If there are particular areas you need help with, feel free to skip to any of the following sections:
What is a Reed Switch?
How Does a Reed Switch Work?
History of Reed Switch Technology
Additional Resources

manufacturing a reed switch

Standex Electronics has expert engineers and cutting-edge manufacturing capabilities. Standex is the largest global leader in customer-specific product development and manufacturing services. We produce unique solutions for just about any environment or application. For example, the reed switch is one of our most successful and most widely employed developments. As the world’s largest reed switch manufacturer, we produce more than 700 million reed contacts per year.

What is a Reed Switch?

A reed switch is an electromechanical switching device. The overall structure is simple. Two ferromagnetic blades that are hermetically sealed in a glass envelope. In other words, these components can exist or be used in almost any environment. Furthermore, the glass envelope has a temperature coefficient that exactly matches the Nickel Iron (NiFe) reeds.

A simple magnet interaction opens and closes the reed contacts. More precisely, the presence (or absence) of a magnetic field produced by a permanent magnet or electromagnetic coil causes the contacts to open or close. No power is consumed when the switch contacts are open. The simplicity of this structure and operation allows reed switches to have no wearing parts and perform reliably as a “switch” for billions of operations in numerous industries. Today, all major market segments use reed switch technology. For example, test and measurement equipment, medical electronics, telecom, automotive, security, and appliances all use reed-based switching components. So it’s no wonder, the reed switch growth rate is stronger than ever, where the world output cannot stay abreast with demand.

What is a reed switch

A reed switch showing the detail of reed contact area and components of a reed switch.

How Does a Reed Switch Work?

Reed switches work by reliably switching billions of operations using a simple magnet interaction to open and close contacts. First, the basic operation of a reed switch happens when it is brought into proximity of a permanent magnet, and the individual reeds become magnetized with the attractive polarity of the magnet. Second, when the external magnetic field becomes strong enough, the magnetic force of attraction closes the blades of the reed switch. Third, the magnetic field produced by the reed blades dissipate when the magnetic field is withdrawn.

Most importantly, since any residual magnetism on the reed blades would affect the opening and closing behavior. Therefore, the reed blades are annealed and processed removing any magnetic retention. Click here to see a reed switch in action.

How a reed switch works with a permanent magnet positioned parallel to the switch and moving perpendicular over the center of the switch.

The permanent magnet and reed switch are parallel to each other, influencing the center magnetic lobes. Positioning the magnet further away from the reed switch will focus on the center lobes and produce a single open and closure as the permanent magnet moves parallel to the plane of the reed switch.

History of Reed Switch Technology

Bell Labs first invented the reed switch in the late 1930s. Although they have been in use for decades, not much has changed in regards to the operating principles of reed switches. In the 1940s, sensors and relays widely used reed switch technology. Moreover, early electronic and test equipment used reed switch components to perform stepping and switching functions. In the late 1940s, Western Electric central office telephone switch stations began using reed relays. Reed switch technology greatly improved telecommunications both in the 1940’s and still today.


Due to their exemplary performance, new uses for reed switches continue to rise at a quickening pace. The Standex team is standing by to fill the ever-changing needs of customers across industries, and across the world, through our Partner, Solve, Deliver® approach. Get in touch with our team at to learn more about our carefully engineered solutions.

Additional Resources

For a deeper understanding of how a reed switch works download our Reed Technology Databook.

Reed Switch Technology Databook

This databook provides a deep dive into what a reed switch is and how a reed switch works. Gain extensive knowledge of various applications, features, and benefits.

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