420i The 420i loop powered isolator is a 0(4)-20mA direct current isolator. The isolator derives its power from the input signal and therefore requires no external power supply. Two other variants are also available. The 420i-1 which has a built in precision 250� resistor to give a 1-5V output, and the 420V which gives a 0-10V output from a 4-20mA input, whilst dropping just 5V from the input loop. 420-TW The 420-TW series of isolating terminal blocks can replace standard DIN-rail terminals to provide input isolation, signal conversion and excellent RFI and noise rejection. Input available include thermocouple, RTD, current and voltage and the standard output is 4-20mA. For thermocouple inputs, internal rotary switches allow the user to select virtually any type of thermocouple and the temperature range required.