Off hook disables PL and the metal thingy on the back of the microphone

Off-hook Disables PL

In the MOTOTRBO CPS, under General Settings is the above tick box that's ticked by default. In this mode, the radio will look at the hook state of the microphone.

The stud (red) and ring (green).

If you have a look at the back of any Motorola mobile microphone, there is a hangup stud but there's also a ring around it. Now when the microphone is hung up on the hangup clip, the ring and stud are shorted and the radio regards the state as "on hook".

If the user pulls the microphone off the hangup clip, the radio now regards this as being "off hook" and in this case, PL (CTCSS or DCS) will be defeated - meaning the programmed PL/DPL code is no longer needed to un-mute the radio.

 A hangup clip

This is applicable to both analogue and 5-tone channels.