Source google image: https://image.made-in-china.com/202f0j00NnoQyHrPrhke/Passive-2-Wire-Potentiometer-Signal-to-4-20mA-Signal-Isolation-Transmitter-ISO-R9-4-20mA.jpg
R 9 isolation
Source google image: https://image.made-in-china.com/202f0j00NnoQyHrPrhke/Passive-2-Wire-Potentiometer-Signal-to-4-20mA-Signal-Isolation-Transmitter-ISO-R9-4-20mA.jpg