Sony PCV-L640 Manuel

When you connect a microphone or headphone to your computer, attaching a 
ferrite core will reduce electrical interference.

Attach the (supplied) ferrite core at the end of the headphone or microphone 
cable closest to the computer.

Wrap the cable through the center of the ferrite core.

The following illustration shows how to attach the ferrite core when you are using 
both a headphone and a microphone.

The LCD and keyboard cables already include a ferrite core. Do not remove the 
ferrite core from these cables.