A radar level gauge for determining the filling level (L) of product in a tank , said gauge comprising: a housing (14; 114) with a housing wall enclosing a compartment providing explosion proof protection; RLG circuitry located inside compartment, said circuitry in use having an available electrical and/or thermal energy incompatible with intrinsic safety requirements; a signal propagation device (11; 111) located outside said compartment, said signal propagation device being adapted to direct a microwave transmit signal toward said product and return reflections thereof from a surface of said product; an explosion proof first signal passage (16; 116) in said housing wall, said first signal passage providing a transmission line for said microwave transmit signal between said RLG circuitry and said signal propagation device; an explosion proof second signal passage in said housing wall, said second signal passage providing a two-wire interface for electrically conductively connecting said radar level gauge to an intrinsically safe system located externally of said radar level gauge, to provide at least one of: communication between said radar level gauge and said intrinsically safe system, and power supply to said RLG circuitry; and an electrical barrier connected between said RLG circuitry and the two-wire interface, characterised in that said electrical barrier prevents energy or voltages in said RLG circuitry from compromising the intrinsic safety of an intrinsically safe system connected to the two-wire interface, and wherein the electrical barrier includes at least one diode connected in parallel between lines of the two-wire interface, thereby preventing negative voltages at the two-wire interface. a housing (14; 114) with a housing wall enclosing a compartment providing explosion proof protection; RLG circuitry located inside compartment, said circuitry in use having an available electrical and/or thermal energy incompatible with intrinsic safety requirements; a signal propagation device (11; 111) located outside said compartment, said signal propagation device being adapted to direct a microwave transmit signal toward said product and return reflections thereof from a surface of said product; an explosion proof first signal passage (16; 116) in said housing wall, said first signal passage providing a transmission line for said microwave transmit signal between said RLG circuitry and said signal propagation device; an explosion proof second signal passage in said housing wall, said second signal passage providing a two-wire interface for electrically conductively connecting said radar level gauge to an intrinsically safe system located externally of said radar level gauge, to provide at least one of: communication between said radar level gauge and said intrinsically safe system, and power supply to said RLG circuitry; and an electrical barrier connected between said RLG circuitry and the two-wire interface, characterised in that said electrical barrier prevents energy or voltages in said RLG circuitry from compromising the intrinsic safety of an intrinsically safe system connected to the two-wire interface, and wherein the electrical barrier includes at least one diode connected in parallel between lines of the two-wire interface, thereby preventing negative voltages at the two-wire interface. <EOS>