Russ, Than ks for your reply. Would this also apply to the 'cylinders' on the DC power feed to the laptop? Preston Russ Poffenberger said the following on 22/05/2007 11:57 AM: > Preston, > > This sounds like a ferrite core or bead. These are used to suppress RF > (Radio Frequency) signal interference that might be present on the > wires. Without these beads, the signals would travel down the length of > the wire and possibly emit radio interference along the path of the wire. > > These ferrite beads are usually made of powdered iron that has been > pressed together into the desired shape. > PCBUILD's List Owners: Bob Wright<[log in to unmask]> Drew Dunn<[log in to unmask]>