A system and method for loading software identifies versions of software modules to be loaded. More specifically, circuits and methods are provided for driving power amplifiers with BJT switching devices to achieve highly efficient switch-mode operation at millimeter wave frequencies. A photodetector interface circuit is connected to the photodetector output and converts the current signal to a signal indicative of the detected light without undesirable electrical offsets, such as manufacturing, production and temperature offsets. Depending on the application, the geartrain may be a planetary epicyclic or an eccentric hypocyclic type. During rotation of the magazine, each slide can be aligned with the driver. A call-in feature is also provided as well as a system query log.