The little plastic at the end of a data cable does something important for your devices.

You’ve ever noticed that plastic band or thing or whatever it is at the end of digital cables; and probably wonder what on Earth it even is. You sometimes even get annoyed with it but nevertheless, that thing is placed right there on the cable for a very special purpose. Its not some fancy designing by computer engineers. It is called a Ferrite Bead or Cloke. Without it, your electronic devices may “choke to death,” electronically.

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Electric Blockade, Not Ornament

Ferrite bead — also known as a ferrite choke — is a passive electric component that’s placed on the ends of digital cables to suppress the high frequency noises in an electronic circuit. It is a special type of electronic choke. Ferrite beads employ a high frequency current dissipation to build high frequency noise suppression to electronic devices. It prevents electromagnetic interference (EMI) in two directions: from a device or to a device.

A conductive cable may act as an antenna — if the device produces radio frequency energy, this can be transmitted through the cable, which acts as an unintentional radiator. In this case, the bead is required for a regulatory compliance in order to reduce EMI. Conversely, if there are other sources of EMI, such as household appliances, the bead prevents the cable from acting as an antenna and avoid receiving interference from these other devices.

Your Electronic Highway Checkpoint

This is very common on data cables (computing devices) and on medical equipment. Large ferrite beads are commonly seen on external cabling. Various smaller ferrite beads are used internally in circuits — on conductors or around the pins of small circuit-board components, such as transistors, connectors and integrated circuits. You have no idea it was that important, right?

In other words, a ferrite bead acts as a customs checkpoint. Just as highway patrols are set up on major roads to check the ease of motor activities, a ferrite bead also does quite a similar thing by checking the flow of data signals that might not be needed by a connecting device. In a pure inductor, this does not dissipate energy but it produces a reactance that impedes the flow of higher frequency signals. This reactance is commonly referred to simply as an impedance — although the impedance can be any combination of resistance and reactance.

A ferrite bead can be added to an inductor to improve it’s ability to block unwanted high frequency noise, in two ways. First, the ferrite concentrates the magnetic field, increases inductance and therefore reactance, which impedes or ‘filters out’ the noise. Second, if the ferrite is so designed, it can produce an additional loss in the form of resistance in the ferrite itself.

Beads On, And Get Wired Up

Image: Shutterstock / iStock / Getty Images Plus

By engineering, ferrite beads are also used as a passive low-pass filter by converting radio frequency energy to heat. The geometry and electromagnetic properties of the bead is coiled up in a way that results in an impedance for high-frequency signals. The energy is either reflected back up the cable, or dissipated as low level heat —  only in extreme cases is the heat noticeable.

So there you have it, the importance of that band on data cables. Next time you find them annoying or somewhat, remember they are there for the safety of your own device.

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Written by: Nana Kwadwo, Wed, Jan 02, 2019.


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