Originally posted by THoog The 'A' lenses do have an electrical connection of sorts - there is a pattern of either plain metal or insulated dots on the lens mount that touches the contacts on the camera when the lens is locked in place. This tells the camera that the lens is attached, and what the range of apertures for the lens are. From this, the camera can determine how far to move the aperture arm to get the desired aperture.
To explain further, if the camera sees all of the contacts shorted it will assume you are using an M series K mount lens. If it sees none of them shorted, it assumes you have no lens mounted.