i saw an even simpler ckt .. sorry the dia is not with me now ...i'll try explaining it , it consists of series of transistors connected in chain ie EC-EC-EC....(depends on the length of password, all PNP) , now the bases are connected to vcc through a capacitor , and the password switches are connected to the base of transistors through a resistor to previous trans: Collector. now the working of the ckt is like this.
the user needs to press the switches sequentialy so that the cap: gets charged and the transistor turns ON, if second has to turn on , the first should be turned on, the connection is like that . so when the user presses the correct sequence , all the trans: will be conduction(for some time) and enable a relay or some thing like that. the password keys are distributed in a keypad . and also to increase security some false keys are wired so that when they are pressed , it discharges the capacitor . It makes that only the correct key combination in correct speed will operate the lock.
hope u understand the description