Gates

There are a lot of different Gates from the BuildCraft mod.

Gates have been added to the mod to provide a method of controlling things from a distance. They can do all sorts of useful things, like detect when an item is traversing the pipe, detect the state of adjacent machines and containers.

Gates are crafted with Assembly Table from their respective Chipsets and, with the exception of the Basic Gate, they also require Pipe Wires.

Gate types
Additionally, once crafted, gates can be transformed using regular crafting to/from AND to OR in the same class with the addition of a new redstone chipset.
 * BuildCraft 3.1.5
 * Basic Gate (1 Slot)
 * Iron AND Gate (2 Slots)
 * Iron OR Gate (2 Slots)
 * Gold AND Gate (4 Slots)
 * Gold OR Gate (4 Slots)
 * Diamond AND Gate (8 Slots)
 * Diamond OR Gate (8 Slots)
 * Buildcraft 3.1.6+
 * Autarchic Gate
 * Autarchic Iron AND Gate
 * Autarchic Iron OR Gate
 * Autarchic Gold AND Gate
 * Autarchic Gold OR Gate
 * Autarchic Diamond AND Gate
 * Autarchic Diamond OR Gate

Normal vs. Autarchic?
Autarchic gates when place on a pipe and set to have the energy pulser effect it will act like a redstone engine on that pipe. So if place on a wooden transport pipe connected to a chest, it would pump items out. Place on a wooden waterproof pipe, it would pump the liquid out. Placing an Autarchic gate on any other type of pipe would have no additional effect beyond that of a normal gate.

AND vs. OR?
(Note: This only applies when using the redstone signal effect.)

If you want the gate to output a redstone signal when more than 1 cause is true then use an AND gate. If you want to output a redstone signal when any of the causes are true then use an OR gate.

Pipe Wires
Pipe wires, an alternative to redstone, can be used to send signals when certain conditions are met by the gates. However, only Iron, Gold and Diamond gates can send and receive signals by the pipe wires.