A staple gun comprising a main body and a staple injection nozzle for injecting a staple into a target object, the staple injection nozzle including a nozzle body mounted on a staple striking body and a cover plate for removably closing an upper portion of a staple injection path of the nozzle body so as to guide the staple. The valve closure mechanism includes a pulley, a load plate, a cable, and a spring. In at least one implementation, amplitude adjustment of the RF input signals of the one or more power amplifiers may be used to provide transmit power control andor power backoff.