Output conductance of a differential current output type circuit constituting a filter body and having a variable negative resistor connected between differential output lines is automatically regulated. Left and right foot platforms are movably mounted on respective foot skates and constrained to move up and down in reciprocal fashion. The portable terminal allows a stylus pen accommodating space to be used as a space for receiving a battery pack such that a battery pack with an expanded capacity can be coupled therein. The back-and-forth movement of the slidable gear lock can be as a complement to the tip of the slidable gear lock and teeth of the gear to prolong the operation life of the slidable gear lock, steering gear and the rivet toolrivet nut toolrivet bolt tool. The AUI further can include a barge-in facility.