A device used on a ship to send signals from the bridge to the engine room, or to the station where the ship's engines are controlled from.
It consists of a round dial approximately nine inches in diameter, with a knob at the center, which is used to move an indicator. Actually, two indicators. The indicator needle points at the desired "bell", or nominal engine speed.
Both the bridge and the engine room have an EOT. When the bridge orders a bell by ringing it up on the EOT, the engine room EOT indicates the ordered bell. This bell must then be acknowledged by taking the engine room EOT to the same bell, which indicates to the bridge that the folks in the engine room are indeed paying attention and will start answering the bell.
When an order is given over the EOT, it rings (duh, like a bell). If an order is especially important, the goombas giving it will ring it three times. This is called a "cavitate" bell. The reason it is called that is because the rapid acceleration of the propeller will cause it to cavitate, which is normally a tactically poor idea on a warship (because it makes more noise), but which is okay right now, because we really need to get going faster than we are so a torpedo doesn't hit us or something.
The positions listed are as such:
Where AA stands for "all-ahead", Z means "all-stop", III means "flank", II means "full", I means "standard", B means "back" and BF/BE are "back full/back emergency". There is no such thing as back standard, because it is not standard for a ship to be going backwards. Yes, it does seem bizarre that "all-ahead full" is not the fastest. You'd think it'd be like that.