The DC 24 V power supply connection is used to supply the PT2001-A1 with power.
DC 24 V power connector - 'CN2'
DC 0 V
DC 24 V
The DC 0 V is galvanically isolated from the reference voltage (GND), analog audio and all digital interfaces. The galvanic isolation prevents earth loops and earth bypasses.
The 24 V can be supplied from a cabinet or an external power supply 'Merawex ZSP135 DR-7A-3 40 Ah' PP2004-A1 with a separate cable.