When the electrodes are pressed against the assailant and the trigger is pulled, a high voltage, low amperage current travels from the electrodes through the assailant's clothes into their body.  The pulsed current causes muscles to work extremely fast, depleting them of needed blood sugars.  The entire process only takes a few seconds and once the assailant is hit with the voltage the muscles refuse to work causing the assailant to be temporarily disabled.  This allows the victim plenty of time to escape.