Can anyone shed any light

[Swearwolf]

Found this old part (see pics) in my room earlier, no idea what it is/what it does/how to use it. Any advice? I think it's to do with sound, +rep.

http://i50.tinypic.com/2com0dw.jpg

http://i46.tinypic.com/6z3gas.jpg

[LOLROB]

http://www.tech-faq.com/spdif.shtml