 A major design problem on early units involves the fact that the microprocessor (which is inside the top of each cartridge) lacks ESD protection and is directly connected to the copper pins which normally connect the cartridge to the Microvision unit.If the user opens the protective sliding door that covers the pins, the processor can be exposed to any electric charge the user has built up.If the user has built up a substantial charge, the discharge can jump around the door's edge or pass through the door itself (dielectric breakdown).