Circuit-breaker arrangement (32) in an indicating arrangement (33) forming part of an electrically powered stapler (1). The stapler comprises a stapling head (2) and an anvil (3). The stapling head comprises an interchangeably fitted staple cassette (5) containing staple blanks (36), and the indicating arrangement. The circuit-breaker arrangement is so positioned that it is moved by the staple cassette from a first to a second position when the staple cassette is fitted to the stapling head and when the power supply via the indicating arrangement changes. The circuit-breaker arrangement (32) comprises an input line (22) and output line (23), of which at least the input line is dimensionally stable and resiliency flexible. The input line is impinged upon by an electrically non-conductive region (34) of the staple cassette when the latter is fitted to the stapling head, with the result that the line is moved against its resilient resistance so that the circuit-breaker arrangement switches from the first position to the second position. The resilient resistance returns the circuit-breaker arrangement to the first position when the cassette is removed from the stapling head.