Abstract: The present invention provides for an Ethernet, or similar, communication system safety device for hazardous environments arranged for coupling to an apparatus within a hazardous environment in an Intrinsically Safe manner, including first input means arranged for receiving data signals; first output means arranged to transmit data signals; and an energy limiting means having at least one capacitor, and generally at least two capacitors, arranged to block a DC component of data signals received in the safety device, the energy limiting means being coupled at a first end to the first input means and at a second end to the first output means and arranged to limit the energy of data signals received in the safety device prior to transmission.