Set the switch mode to push to open and connect it across the signal lines. (pins 2 and 3)

releasing the PTT will mute the microphone signal by shunting it.

So, connect pin 4 to pin 2 and pin 5 to pin 3

With a 20 foot cable this may not work very well. if you allowed to modify the base make the same connection internally instead.

Set the switch mode to push to open and connect it across the signal lines. (pins 2 and 3)

releasing the PTT will mute the microphone signal by shunting it.

So, connect pin 4 to pin 2 and pin 5 to pin 3

With a 20 foot cable this may not work very well. if you are allowed to modify the base make the same connection internally instead.