Phoenix Contact 2906824 A surge protection system consisting of a protective plug and base element with an integrated status indicator and disconnect knife is designed for use in 2-wire floating Ex-i signal circuits, such as those with a current loop measuring 0-20 mA, and is compatible with HART (Highway Addressable Random Access Technology) technology. This type of system can be utilized in safety-related circuits that require SIL level 3 compliance.