Video/Audio Distributor.
DS-KAD606P provides 24v – this distributor totally different from normal POE switch. The normal POE provides 48v.
If DS-KAD606P not used, your option is power the door station and monitor using 12volts power supply. Make it sure you provide power to door station and monitor first before plugging to POE switch. (Once 12v provided the POE power automatically disabled)