What are these things on cables for?

[Bob A Job]

Recently ive noticed most cables have a heavyweight cylinder just before the connection like this . what is it for, it seems to be on everything from computer cables to headphone connectors.

Thanks in advance

[Bob A Job]

the link didnt work try here

[rojash]

It's a ferrite inductor which reduces high frequency emissions

[Bob A Job]

Possibly the fastest answered question on the 'Bank'
Thanks rojash

[heathfield]

Just to elaborate a bit on rojash's answer - They are filters that block any noisy or spiky voltages that could be present on the cable. Example - the d.c. power cable for your laptop. You wouldn't want spikes on your otherwise smooth supply as they just might corrupt things inside the computer. More and more devices these days use computer type chips, (digital cameras, mp3 players, mobile phones, etc), and these chips can be susceptible to damage by a noisy or spiky power supply. Hence the filters.