<P> A ferrite bead or ferrite choke is a passive electric component that suppresses high frequency noise in electronic circuits . It is a specific type of electronic choke . Ferrite beads employ high frequency current dissipation in a ferrite ceramic to build high frequency noise suppression devices . Ferrite beads may also be called blocks, cores, rings, EMI filters, or chokes . </P> <P> Ferrite beads prevent interference in two directions: from a device or to a device . A conductive cable acts 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 regulatory compliance, 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 receiving interference from these other devices . This is particularly common on data cables and on medical equipment . </P>

What does a ferrite core do on a cable