The T3-Micro is a Tracker3 in a USB dongle form factor, presently in beta testing.
Pinout (3.5mm TRRS connector, starting with tip):
Tip - Audio in (from speaker) Ring - PTT (open collector) Ring - Audio out (to mic) Sleeve - Ground
In place of the HT jumper used on the OT3m and T3-Mini, the T3-Micro uses the command HTPTT ON/OFF to set the PTT mode. Most handhelds, except for Kenwoods and Chinese imports like Wouxon, Puxing, and Baofeng, should use HTPTT ON.