Technical FILTER & FUSE BOX 7A behind the stereo - what is it for?

[PeterPolak]

Hi folks,

I removed the old stereo from my seicento and while messing up with cables I managed somehow to blow the 7A fuse in the little black plastic box that has "FILTER & FUSE BOX 7A" written on it. I don't seem to be able to buy such fuse around here so I'm asking a question: does anyone know what this little black box is for? Do I need it for my stereo? There are two wires coming into the box - yellow and black - and two wires coming out of it (again yellow and black). The fuse was between the yellow wires.

Thanks for any help!

 

[cc1]

7A is the fuse rating. 7 Amps.
The filter is to help stop alternator noise going to the stereo.