This is a story my teacher told me almost 10 years ago.
A computer component had been returned from the customer.
It was a hard drive and on it was a sticker with the note "no dial tone"

The fun started when I actually found a harddrive producing the noise you can hear in the linked audio file.
My teacher and I had a real good laugh over this

http://hem.spray.se/hanzzzon/harddrive.mp3

I even had a hard drive that sounds even louder and much clearer, but didn't record it. Yes, this "feature" ist really funny