Geek Trivia

What Are The Plastic Lumps Found On The Ends Of Computer Cables Called?

EMI Loops
Ferrite Beads
Impedance Rings
RF Clamps
Who Was The Only Civilian Astronaut In The Gemini Space Program?

Answer: Ferrite Beads

That clunky cylinder of hard plastic on the end of many of the cables you’ll find around your home and office–USB cables, VGA cables, and so on–has a specific function.

Inside the hard plastic casing is a chunk of ferrite-infused ceramic designed to suppress high-frequency noise. Essentially the ferrite bead acts as a passive low-pass filter that both absorbs energy or reflects it back into the cable. The majority of energy is absorbed by the bead and then released as tiny amounts of heat into the surrounding air.

Why is it important to suppress the high-frequency noise? The noise suppression serves two primary purposes. First, it prevents electrical noise generated within the computer from interfering with other components–so, for example, interference from the computer doesn’t interfere with the performance of your monitor. Second, it prevents the electrical and radio energy from leaking out and interfering with surrounding equipment like television sets and radios.