The "free hand" consists of a button to answer / end with a small microphone.
The connector is a 3.5 stereo jack + microphone as found on many smartphones.
I tested it by listening with a PC (connection to the headphone jack) and an iPhone 4s.
The sound reproduction is good, both in the acute that serious.
The cable is intended for use with a smartphone or MP3 player, so it's a little short to be connected to a computer under the desk or a hi-fi, but enough for a laptop.