A punching-depth adjusting device for use with a nailing gun is adapted to cooperate with the conventional connecting device and has a scale sleeve, a sleeve, and a resilient C-ring. The device rests upon the floor and comprises a vertical member extending upwardly which has an upper end and a lower end. A display assembly includes a pushbutton switch and one or more light emitting diodes that indicate which time period is selected mounted to a circuit board. The third analog switch drives on when the first and second analog switches drive off, and outputs the second voltage to the series connection node of the first and second analog switches. , Galois linear feedback shift register in combination with digital comparators and an adder. For a test mode of the storage drive, a write current driver circuit and a test current sensor are electrically connected to the write head, wherein the test current sensor generates a sense signal indicative of a degree of a flow of a test current through the write head to thereby facilitate a detection of any presence of an open write condition of the storage drive.