Abstract: To protect an encapsulated fuse (9) within a wholly enclosed sealed safety barrier having a first voltage limiting circuit (10) and a current limiting circuit (15), an externally accessible high current interrupter (5), such as a fuse, positive temperature coefficient resistor (26) or circuit breaker (27) is connected in series with an input terminal, and further serially connected with a second voltage limiting circuit (6) connected downstream of the interrupter and across the safety barrier circuit, the second voltage limiting circuit having a voltage limiting response characteristic which is, preferably, the same as the first voltage limiting circuit within the barrier, and the interrupter having a response threshold which is at least as high, but may be higher than the fuse (9) encapsulated within the circuit.

Abstract: The barrier input and output each have two terminals. In at least one connection between the barrier input and the barrier output, there is an electronic in-line control element having a control input as well as, in series with the in-line control element, a current sensing element that emits an output voltage corresponding to the current. A control circuit having a control input controls the conductive state of the in-line control element and to this end receives the output voltage of the current sensing element. In accordance with the invention, to obtain a steeper limiting characteristic, the control voltage for the control circuit is the sum of at least part of the output voltage of the current sensing element and at least part of a voltage corresponding to the voltage drop in the in-line control element.