Distribution Transport Pipe
For example, if you input 10 pieces of Redstone Dust, and have one input and 5 outputs, under equal settings, 2 Redstone Dust would go out each output pipe. You could change the ratio to have the output split differently (6:2:1:1, 3:3:2:2, etc).
Note: Its been reported on some multiplayer servers that opening the pipe's GUI can cause the server and/or game to crash.
To use a Distribuiton Transport Pipe, right click it whilst not holding any other pipe or a Wrench (BuildCraft). Each colour in the GUI corresponds to 1 of the outputs. The maximum amount is 1000, and the minimum zero.
Note: While it is possible to disallow backflow by setting the values to 0, there must always be 1 viable output with a value greater than 0. Trying to set every colour to 0 will crash your game.
If you make a set-up which has multiple outputs but only 1 input, you can set each of the colours(except the input, which is 0) to 1. The pipe will distribute items down the path evenly, not randomly. This could be used to send 1/4 of your iron into a furnace to make Refined Iron, and send the rest into a chest or a rotary/macerator, for example.
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