The Redstone Repeater is a vanilla block that has three main functions: acting as a repeater, a diode, and/or a delayer. The block repeats signals it receives like a network bridge, so that using two not-gates every 15 blocks is no longer necessary. Signals are also accepted only in some directions, allowing the block to function much like a diode in an electrical circuit. It also delays the signal by 1-4 ticks (selectable) so that long timing circuits of inverters will not be required for timed mechanisms any longer. In Tekkit, it is mostly used in crafting recipes for the RailCraft mod.