The original Ham Standard counterweight two position props had a ten degree pitch range. Oil pressure took them to low (fine) pitch, counterweights to high (coarse) pitch. Pilot could select low pitch for takeoff, high pitch for cruise. Once in a set position, RPM would vary dependent on throttle and airspeed.
When they needed a "constant speed prop" they added a governor, the props got a fifteen degree pitch range and a big spring inside to help movement. Pilot could select his RPM within the governing range and if sufficient power was there to take it to that rpm. The constant speed name meant it would maintain the selected rpm despite throttle movement or airspeed changes. prop pitch would change to maitain that rpm.
Ham Standard Hydramatics had oil pressure on both sides of piston. You could select your rpm as with the counterweight constant speed prop.
Curtiss Electrics were different. You could manually toggle the prop pitch to whatever pitch you desired and there it stayed. RPM wuld vary with throttle. If you selected Automatic, it followed either a governor mounted on the engine or a electric master motor for synchronzation depending on the aircraft installation. The governor or the master motor could be set for the desired rpm and you now had a constant speed prop.
One peculiarity, at least on Connies, the Ham Standard Hydromatics prop control switches had three positions "Increase" "Decrease" and "Automatic" - There was no OFF position. The Increase/Decrease referred to RPM selection. Curtiss installations the prop switchs had four positions "Increase" Decrease" OFF" "Automatic" BUT the Increase/Decrease referred to prop pitch - effect was direct opposite of the Ham Standard markings. When you worked mixed fleets you had to watch what you were doing. On the Curtiss you selected the rpm you wanted with a Master Motor lever and when you put the prop switches to AUTO the engines slaved to the master motor.