Rail Transmitters SITRANS TR200, TR300, and TW varies in the wiring technology. The TWO-Wire TR-Series transmitter is installed in cabinets, or applicable housings in the field. The user can maintain several sensors from one point. 4-20mA-signal and auxiliary power will be lead over two wires. The FOUR-Wire TW-Series transmitter is installed in the control room and allows universal use. Connected directly with auxiliary power they support several output signals, relay function and further features.