Description
The Wire Guard is clamped over the headset wire above the plug, which is inserted into the phone. The bead uses a ferrous composition based material which interacts directly with the high frequency energy and blocks it effectively while allowing the voice signal to pass through to the earpiece unimpeded. The case is a nylon resins which can come in black or white.

How it works
The effect of magnetic material on a conductor current flowing through a conductor creates a magnetic field around it. Transfer of energy between the current and the magnetic field is effected through the "inductance" of the conductor - for a straight wire the self-inductance is typically 20nH per inch. Placing a magnetically permeable material around the conductor increases the flux density for a given field strength and therefore increases the inductance.