In Germany, the thing I'm familiar with is a small lever that you turn left/right to control the temperature and (depending on whether it's mounted horizontally

In Germany, the thing I'm familiar with is a small lever that you turn left/right to control the temperature and (depending on whether it's mounted horizontally or vertically) either up/down or to/fro to control the flow rate: https://commons.wikimedia.org/wiki/File:Einhebelmischer.jpg https://commons.wikimedia.org/wiki/File:Einhebelmischer.jpg