In 1966, the well-known model engine manufacturer Webra launched a small proportional system, the Webra “Picco”, which worked according to the flutter principle, i.e. the rudder to be controlled constantly oscillated back and forth and moved in the controlled direction when a control input was made.
Only one function could be controlled.
Go to the Webra History: https://classicpattern.com/webra/?lang=en