The HV-Transformer is used to turn Extreme Voltage (EV) EU current into High Voltage (HV) and back. It has limited use since the only machine that outputs a voltage higher than 512 EU/t is a Nuclear Reactor, and only under certain conditions.
Normally, the HV-Transformer takes an input up to 2048 EU/t on the face with three dots, and outputs 512 EU/t on any face with one dot. When the transformer is receiving a redstone signal, this is inverted: The three-dot face will output 2048 EU/t, and any of the one-dot faces will take an input up to 512 EU/t
|Input (three dots)||up to 2048 EU/t|
|Output (one dot)||512 EU/t|
|Input (one dot)||up to 512 EU/t|
|Output (three dots)||2048 EU/t|