A TRRS extension from the iPad is split into mic and audio out (cheap splitter from Amazon). Bonus points for using a vintage Apple audio cable (top middle). Mic for Siri and handsfree calling plugs in here. I used an audio cable rather than rely only on the USB connection to the deck, because there is no software volume control for the Lightning connector – it outputs at a set volume that can't be modified. I didn't want to have to reach over to the deck to adjust audio volume!