The containment field is complementary to the Force Field - while that keeps things out, this keeps them in. Note that hostile mobs which fire projectiles, like Skeletons and the Wither, can still hit targets outside the field without leaving it themselves. This machine needs a clear view above it equal to the selected radius.
Required Power: 131072W
Range = 2+(Power-131072)/8192 m
Power Input: Any side
Requires 524288W to restrain a Wither and 2097152W to restrain an EnderDragon