The TP-DC-1248GDX2-HP is a unique high power PoE injector with Dual 802.3af/at compatible outputs. This means that two devices can be powered from a single PoE injector. The data path between the devices is handled by the injector so no PoE switch is required. This model runs on 12VDC. The total combined output is up to 42W. They have two DC inputs for connecting 2 power sources, like a primary and backup power source. They have various protections for short circuit, overload and surges caused by ESD or lightning. The built-in surge protection protects sensitive connected devices from damage due to surges on data and PoE lines. All 8 wires are protected. The input voltage and output voltage are isolated to avoid any grounding or negative voltage issues.