XLR Cable

Three pins: a ground, and two conductors carrying the same audio with one of them inverted. At the far end the receiving gear flips it back and sums the two, so any interference picked up along the run cancels itself out. That is why a microphone can sit thirty metres from the recorder with no hum in the signal. The same cable carries phantom power, the 48 volts a condenser microphone needs, sent up from the mixer or interface. The connector locks. Studios standardised on it partly for that, because nobody kills the audio by catching a cable with their foot.