A firmware control method for the optimized use of a single AD converter to measure multiple analog signals with asymmetric requirements on sampling rate including a lookup table design procedure and an acquisition algorithm. The battery current limiter monitors measured battery current and torque commands. An impaling tool having a generally conical leading end is carried on the hammers radially inwardly of the edges to project a generally tangentially predetermined distance forwardly and provide an initial rigid work contacting portion ahead of and cooperating with the knife edges. Another six-port device implementation is a network of transmission lines connected in series.