Activity indicator (RU)

It's just a LED indicates squelch state. Just use signal from pin 2 and invert it:

Components

NPN transistor (i.e. 2222)
3 resistors 1k
LED

Step 1

Unmount PTT front panel and drill a hole for LED

Step 2

Look for a hidden cut wire from the second pin of RJ45

Step 3

Make it longer

Step 4

Mount components

Step 5

Enable REP-M mode and test it:

No activity

Someone on the air