The project is to fashion a metallic box-like safe that will be locked with a 4 digit combination digital lock based on LS7220. The key pad should have 12 buttons. (Actually, i'm coupling the circuit, i'm not the inventor). If the right combination of keys are pressed, the lock opens and remains open for some seconds and then locks again. My major constrains are that i can't see the LS7220 and an electronic lock for it in Nigeria. Diagram **broken link removed**