4-072 series :
The earphone connects to the PTT switch in which the microphone is hidden. The second wire extends from the PTT switch to the plug that connects to the two-way radio headphone jack.
For two-way radio beginners, please don///'//i/t put the earphone into or out of the radio when it is functioning.
Two wires extend from PTT switch, one to the earphone and the other to the plug that connects to the headphone jack of two-way radio;
This earpiece can provide several plugs: