Bellcrank

A typical 90-degree bellcrank consists of an L-shaped crank pivoted where the two arms of the L meet.

A typical 180-degree bellcrank consists of a straight bar that pivots at or near its center.

Many applications do not change the direction of motion but instead amplify a force "in line", which a bellcrank can do in a limited space.

Bellcrank mechanisms were installed at the top of entryway stairs in multi-unit Victorian and Edwardian homes (c. 1890 to 1930), particularly in the San Francisco Bay Area, to allow residents to open and close the doors remotely so they would not need to walk down the stairs to welcome guests.

[2][3] The motion from a Bowden cable is translated by a bellcrank to a push rod, which selects which portion of the epicyclic gears are driven by the bicycle's rear sprocket.

Illustration of a bellcrank from the 1908 Chambers's Twentieth Century Dictionary
Front suspension system of the Tramontana ; note the bellcranks coupling the suspension pushrods to the coilovers