RAIL-MOUNT TEMP TRANSMITTERS When connected in the 4-20 mA loop, Sitrans TR200 and TR300, designed for rail mounting, need no additional power supply. TR200 is configured using a PC, and TR300 uses a HART interface. Both feature a diagnostics LED that indicates the function status, which quickly detects open or short circuits, so they can be corrected. The temperature transmitters support all standard RTDs and thermocouples, as well as resistance and voltage inputs.