Power boats are typically Fast electric or internal combustion, (ignition engine or glow plug R/C engine based) and some are steam powered (conventional type, and also flash steam). (At one time some boats used engines working on the compression ignition principle. These were not diesels in the true sense of the word but the modelling fraternity frequently referred to them as such. A few enthusiasts still operate such engines.) The power is commonly used to rotate a submerged propeller, aircraft propeller or jet which in turn provide the thrust to move the craft. Typically power boats have two controls, rudder, outboard motor or stern drive and throttle control. Powered scale boats will often have additional remote-controlled functions to improve realism, e.g. sounding fog horns, rotating radar antennae etc. Some of the more sophisticated powered racing boats may also have additional remote-controlled functions. These may include remote mixture control allowing the driver to optimise the fuel/air mixture during a race. Another function occasionally implemented for racing boats using a surface piercing propellor is remote control of depth or angle of thrust. There are three main types of power boat. RTR(ready-to-run), ARTR(almost-ready-to-run), and kit versions are available. All thoroughbred racing boats are made from kits and the builders add their own gear and radio.