This ICOM offers accessory connector with all necessary signals present:
To interface Digirig we’ll need to homebrew an audio cable:
pin 3 → 3.5mm TRRS ring2 (RIG_PTT)
pin 4 → 3.5mm TRRS tip (RIG_AFOUT)
pin 5 → 20K resistor → 3.5mm TRRS ring1 (RIG_AFIN)
pin 8 → 3.5mm TRRS sleeve (GND)
The resistor is suggested in this page as a way to allow the regular mic to continue functioning while digital modes interface is connected.