I have a piece of hardware that my grandma gave me along with her old laptop. I have no idea what it is and neither does anyone I know. It has a mono 3.5mm plug on one end, but plugging it into a headphone jack does nothing. Same result with a microphone jack. It has a 16 foot long cable. Pictures below.
Can someone please tell me what it is, what it does, and how to use it?