What are the supported inputs and outputs of FF positioner

Field Instrumentation
1

Hart positioner supports 4-20mA input and 3-15 psi output then what about the FF positioner

2 
HART is just a communication protocol
4-20mA is a instrumentation, current input signal.

FF does not use current signal as instrumentation signal. It is a binary/digital signal code FF positioner input signal is digital PV and output is 3 to 15 PSI