US Patent 7580237 Systems and methods for immobilization with repetition rate control

An apparatus impedes locomotion by a human or animal target by conducting a current through the target. The apparatus includes a battery, a circuit, and a processor. The circuit charges a capacitance to a predetermined voltage and discharges the capacitance to provide a pulse of the current. Charging occupies a first interval having a duration, the duration affected by an operating condition of the battery. The processor controls the circuit to provide a first series of pulses of the current, the first series having a first pulse repetition rate, the first pulse repetition rate being compensated by the processor for variations in the duration of the first interval.