... II (two-line system, 12 V power supply), Smith-III (two-line system, 24 V power supply), Smith-IV(three-line system , power supply 5 ... V) , Smith –V (three –wire , 12 V power supply), ... : -40 ~ +65°C Feature1, a three-line system (power line is the signal line and the power line and ground).2, non-contact, sending letters ...