Separate microphone signals through phantom power
Your red signal wire is actually two wires, carrying a balanced audio signal (when one wire goes positive, the other goes negative).  The +48 V phantom power is fed via resistors to both signal lines so there should be no net audio signal at the phantom power supply.  The negative side of the phantom power is connected to the cable shield.

The circuit is something like this:







simulate this circuit &ndash; Schematic created using CircuitLab