Intercom with 4 channels, base station

I made a simple Intercom analog system for vision director and 4 cameramen using common 3 wires, 3 pins XLR audio cables. The intercom is bi-directional, so everybody hears everybody.

This is the base station, the belt pack can be found here:
https://www.printables.com/model/764218-intercom-4-channels-belt-pack