A thickness detecting system for a paper shredder having a lever arm extending into the shredder's throat. One or more sensors may be in communication with the lever arm and configured to measure the rotation of the lever. A first maximum thickness and second maximum thickness may correspond to the paper inserted into the throat before and during shredder, respectively. Circuitry may reverse the motor when the thickness is exceeded to ease the removal of the paper and to prevent further shredding. A touch structure and the preferential power supply switch may be used to engagingly interact with each other, so that the motor can be switched off when the plate is selectively positioned to close the paper feed opening, can be switched on when the plate is selectively positioned to open the feed opening, and can be switched off when unexpected items are introduced into the feed opening.