This sits between an ASCII keyboard and the Apple II to 'change' the ASCII values to whatever values you want.I originally built this to fix a specific keyboard with a damaged controller, but I feel I've designed it in such a way that one could use it to add alternate layouts or modes to any keyboard. You could change to the DVORAK layout, or add a CAPS mode for example.Each of the jumpers tie the inputs of the inverter to +5v, resulting in LOW signal at address lines A7, A8, A9, A10.Modifier keys when pressed are expected to GND a line that is tied to +5v with a resistor when the key is not pressed.This wire coming from your modifier control line gets connected to the second pin of the jumper instead of having a jumper there.Hopefully, that is clear. This worked perfectly for me as designed, but as with any of these open and free projects, you are on your own. All the best!