RedPower's Accelerator is a block that, when placed between Pneumatic Tube and Magtube, boosts the speed of the items traveling in the regular tube network to the amount, required for Magtubes to function, but only when it's connected to the source of Blutricity, for example a Battery Box.
Accelerators can connect to the Pneumatic Tubes. Magtubes, or to an output side of any other block (for example, Sorting Machine). It cannot however connect to input side of any machine, so you first have to put a single piece of Pneumatic Tube in between.
When powered with Blutricity, Accelerator glows blue around the sides of the block. It will only boost the speed of items when it is connected to Magtubes on one side. Unpowered Accelerator does not glow and does not boost the speed of items going through it. It however slows down any items coming from Magtubes.
It does not have a specific input/output orientation, but it still needs to be rotated around with Screwdriver in order to be connected to the adjacent pipes.