This small, rather fragile cord ... .. turns out to be necessary to connect a microphone with casqe equipped with 2 jacks (1 sound, 1 microphone) on an iPhone, iMac or Samsung Galaxy Note 2 (my case). Indeed, the iMac for example have no microphone input but input line on which it is not possible to connect a non-amplified source. On iPhone, iMac or Galxy Note 2 (others I do not know), 1 single for his Jack and microphone jack with 3 black rings.