How to use the engineering intercom channel?

I have 2 ATEM talkback converter 4K and ATEM 2 M/E Production Studio 4K. Prod. intercom works fine over SDI. I still need to use the intercom engineering channel. I know the engineering channel is SDI audio channel 13-14 and the prod channel is SDI audio channel 15-16. By default channel 15-16 is used, here is how do I use channel 13-14. Maybe there is an instruction somewhere, maybe I overlooked, maybe I need to check a box? I have searched the entire Internet answer to this question nil.

Blackmagic Talkback audio channels use channels 15+16 for the Production, and 13+14 for the Engineering.
More details about your workflow and what you want, can be usefull...

Blackmagic Talkback audio channels use channels 15+16 for the Production, and 13+14 for the Engineering.
More details about your workflow and what you want, can be usefull...

Hello! We have assembled an OB Van truck with 10 BM Ursa Broadcast G2 cameras. Two ATEM Talkback converter 4k are installed, one in the director's room and the second in the engineering room. At the moment, both work in the prod. channel. I want to separate them so that the director's room works in the prod. line, and the engineering room communicates via the eng. channel.