PTC technology used in CCTV power supply boxes are used to manage the amount current that passes through each channel of power. PTC itself is an over current-protector and is connected in series with the load that is to be protected. During normal operating conditions, the PTC remains in its low resistance state resulting in negligible attenuation to current flow. When a short circuit or over current condition occurs, the PTC will switch into its high resistance state thereby limiting the current flow in the circuit to a point well below the normal operating level. Once the current condition (fault condition) is removed, the PTC will return to it's low resistance self and allow the current to run normal. This technology works great in the field of CCTV, because you don't have to worry about overloads crashing your security cameras. Or better yet you can save your security camera systems from shortages, spikes and surges. Obliviously if lighting strikes the camera, then it is over, but if lighting strikes some where else then you can bet on this device not letting current