相關(guān)元件pdf下載：4081 
this switch will suit the modular burglar alarm circuit. however, it also has other applications. the keypad must be the kind with a common terminal a separate connection f each key. on a 12-key pad, look f 13 terminals. the matrix type with 7 terminals will not do. choose the five keys you want as your code, connect them to 'a, b, c, d & e'. wire the common to r1 all the remaining keys to 'f'. because your choice can include the non-numeric symbols, almost 100 000 different codes are available. the alarm is set using the first four of your five chosen keys. when 'a, b, c & d' are pressed in the right der within the time set by c1 r2 (about 10 seconds), current through r11 switches q6 on. the relay energizes, then holds itself on by providing base current f q6 through r12. the 12-volt output switches from the "off " to the "set " terminal, the led lights. to switch the alarm off again it is necessary to press a, b, c, d & e in the right der. the ic is a quad 2-input gate, a cmos 4081. these gates only produce a high output when both inputs are high. pressing 'a' takes pin 1 high f a period of time set by c1 r2. this 'enables' gate 1, so that when 'b' is pressed, the output at pin 3 will go high. this output does two jobs. it locks itself high using r3 it enables gate 2 by taking pin 5 high. the remaining gates operate in the same way, each locking itself on through a resist enabling its success. if the crect code is entered within the time allowed, pin 10 will switch q5 on so connect the base of q6 to ground. this causes q6 to switch off the relay to out. any keys not wired to 'a, b, c, d e ' are connected to the base of q4 by r9. whenever one of these 'wrong' keys is pressed, q4 takes pin 1 low. this removes the 'enable' from gate 1, the code entry process fails. if c, d e is pressed out of sequence, q1, q2 q3 will also take pin 1 low, with the same result. you can change the code by altering the keypad connections. if you make a mistake entering the code, just start again. if you need a me secure code you can use a bigger keypad with me 'wrong' keys wired to 'f'. a 16-key pad gives over half a million different codes. all components are shown lying flat on the board; but some are actually mounted upright. the links are bare copper wires on the component side. two of the links must be fitted befe the ic.
