1,Adopt to second-wire system 2,Non-contact 3, The long ... II (two-line system, 12 V power supply), Smith-III (two-line system, 24 V power supply), Smith-IV(three-line system , power ... I,II,III<2>Feature1,Adopt to second-wire system 2,Non-contact 3, The long transmission distance, ... +65°C Feature1, a three-line system (power line is the signal line and the power line and ground).2, non-contact, sending ...