A mehanical connection from the actuator to a position feedback cam in the positioner establishes actual position. Three characterized segments on one cam provide application flexibility by establishing various relationships between input signal and actuator position. The relationships provided by the segments are square root, linear, and square. 

The AV3 positioners receive a current input (4 to 20 milliampere) from the control device and convert the signal to pneumatic signal. This pneumatic signal is converted to a pneumatic output that produces the motive force that positions the actuator. Type AV3 fails in place on loss of current input signal. 

The Type AV4 positioner receives an external 24vdc pulse signal and converts it to a pneumatic output. This output produces the motive force that positions the power actuator. The AV4 fails in place on loss of input signal.