The Artech Two Wire Transmitter TX-01, converts voltage, RTD or thermocouple inputs into a 4-20 mA current output.   This eliminates the need for special cables as ordinary wires can be used after the transmitter.  The transmitter requires no separate power supply as it is powered by energy drawn from the current loop itself and is this instrinsically safe when used with appropriate barriers.  The TX-01 can be mounted in a standard thermocouple head in place of the terminal block.  Alternately, it can be fitted into suitable weather proof and/or flameproof enclosures.