This can be used when the switch doesn't support PoE or if the switch has issue negotiating power with the powered device.
Modern corporate switches with a wide range of power settings (LLDP, overload / underload, power budget, eco settings, etc.) are more than ever prone to power delivery issues.
One reliable way to solve these power issues is to use an inline PoE injector between the powered devices (like VisualTarget enclosures) and the switch.
Here is one we recommend that is rack mountable with a large power budget:
Microsemi PD-9024G 24-Port 1000W Power Over Ethernet PoE Injector
Also available from CDW:
CDW - Microsemi PD-9024G - PoE injector - 1000 Watt