The NOT Gate inverts a Redstone input signal which means it will output the opposite of the input. It will output power as long as it is not receiving power from its input side. It works like the vanilla block with a torch on the side.The input is the side facing the player when placed. Use a Screwdriver or Sonic Screwdriver to rotate the NOT Gate by right-clicking.
As with other logic gates, the NOT Gate can be placed on all six sides of a block.
A NOT Gate allows for Redstone circuits to be made for things that should be powered most of the time. For example, they can be used with a Pressure Plate and a Door to create a door that remains open until the Pressure Plate is stepped on, or Pistons that briefly retract when a Button is pressed.
The main uses for NOT Gates are not usually for simple contraptions. The NOT Gate isn't designed to replace an inverted Redstone Torch. It is designed to be tiled with other redpower components. Because it follows the RedPower component structure, it can be used on walls and ceilings whereas Redstone Torches cannot. Also the minimum amount of blocks needed for a Redstone Torch inverter to work is 3. The NOT Gate needs only 1 so in situations where space is a problem the NOT Gate is useful.
NOT Gates can also be used with a Light Sensor. One use for this combination is for lights to turn on automatically at night.
The NOT Gate can be used with a Regulator which emits a constant Redstone signal when a Chest next to it is full or has a set amount of items. With a Chest-Regulator-NOT Gate-Timer setup, the Chest fills causing the Regulator to emit a signal, the NOT Gate turns off and allows the Timer to turn on. The Timer can be connected to multiple Filters to begin sending specific numbers of items to different locations.
As a forcefield trap
It can be used in making a simple forcefield trap shown in the video below.