A selection of hot water extractors are being marketed that range from the large or small canister types with hose and nozzle to those that look more like an upright vacuum cleaner. The basic operation of the steam cleaner vacuum involves spraying a mixture of warm water and detergent into the carpet, washing the fibers and then extracting the solution mixture back out. There are some models that include rotating or revolving brushes that will agitate the carpet for better cleaning.
The earlier styles that were sold consisted of a special wand and nozzle that was used to on wet/dry utility type of vacuum cleaner. The long hose was connected to a nearby hot water source. The detergent came in a small bottle on the wand and was mixed with hot water before being sprayed on the carpet. By using a finger controlled valve, you should control how much water was sprayed in the carpet. Even today, this type of vacuum is still being used.
The more modern designs are more self contained in the sense that water and detergent mixtures are placed into a tank on the machine. This will free you from the long water supply hose.
The main part of an extractor will consist of...