Motorola BDN6726 Single-Wire Earpiece
Model Number:  BDN6726
This black, receive-only surveillance accessory allows the radio user to privately receive messages with the earpiece and is ideal when environments require discreet communication. The intrinsically safe, single-wire earpiece has a standard earphone. It requires the 3.5mm threaded adapter jack BDN6676D that attaches to the radio, unless being used with a speaker microphone.
Number of wires
Does not apply