... second-wire system 2,Non-contact 3, The long transmission distance, square wave output. <1>Smith-I (two-wire ... for remote use. Smith-I,II,III<2>Feature1,Adopt to second-wire system 2,Non-contact 3, The ... power, low level of less than 1 V. 2, letter frequency <2 KHz. 3, Allowable working voltage: DC5V, 12V ... power, low level of less than 1 V.2,Letter frequency<2 KHz. 3,Allowable working voltage: DC5V, 12V ...