FT450 provides one scaled pulse output while the FT440 has two. The FT430 may be powered by external DC power source or an optional AC power supply. The FT440 is a “two-wire” or “loop-powered” device, meaning that the 4-20 mA output signal doubles as its power supply.
FT400 Series Flow Monitor and control
The Seametrics FT400 series flow computers are micro controller-based indicator/transmitters that interface with pulse output
Flow Meter Liquid and Gas Indonesia 