Abstract: A toggle linkage (70) is provided to interact between a pair of levers (50,52) located between a pair of input functions, i.e. a pair of depressible foot treadles (22,24), and a pair of output functions, i.e. control linkages for operating a variable displacement hydraulic machine (31). Each lever (50,52) of the pair of levers is fixed either to a sleeve (58) or to a shaft (63). The toggle linkage (70) includes a bellcrank (72) pivoted about an axis parallel to the axis of the sleeve (58) and shaft (63) and has a pair of abutments or stops (80,84) thereon, each one of which is aligned either with a first one of said levers (50) or with a second one of said levers (52). A link (74) connects a portion of said bellcrank (72) with said second one of said levers (52) limiting the extent of movement of said one of said levers in response to movement of said other of said levers.