THROTTLE.
The Throttle on an engine is the valve which allows the steam to enter or be shut off from the cylinder and should always be left wide open on a governor engine when running, as the governor regulates the quantity of steam required to run it at its proper speed and is much more economical.
There are different styles of valves used for throttles, such as Globe Valves, Butterfly Valves, Disc Valves, etc.
Lunkenheimer Throttle Valve.
The Lunkenheimer is a double disc valve, and is operated by the handle or rod attachment, and requires no lock or ratchet.