Abstract: Disclosed is a panel feedthrough that provides insulation, strain relief, and selective attenuation of electrical signals by ferromagnetic means. The feedthrough consists of an externally toothed sleeve that has a fixed restraining flange, a ratcheting cap and, optionally, an additional locking ring, both of which engage teeth on the sleeve. Panel clamping action occurs when a panel is pressed between the cap or locking ring and the restraining flange of the sleeve. Various combinations of ferrite toroids or beads may be added over the outside of the sleeve and held in place by the cap or locking ring. The clamping of wires, cables or other objects passing through the feedthrough is accomplished by inward deflecting, tapered tabs located at one end of the sleeve. These tabs are deflected into a clamping action by the cap bearing a tapered hole into which the tabs are forced.