code-lock with door opener

ri code-lock with door opener Anyone who has ever locked him or herself out with the frontdoor key inside will appreciate the electronic door-opener described here. If you can memorize four digits in a row and do not mind an investment in I an electric door-opener and a small electronic circuit, you will never need a frontdoor key again. The door can be opened by pressing the keys on a keyboard fitted beside the C1 7-60 0 1I 2 3" 4 5 6 7 8 9 2 I ++ Dl D2 1N4001 R1 DS 8 V BV ti 560n + 06 8V2 D3 04 T„ 0 4x 83564 1N4004 470p zsy 400,8 frontdoor. If you don"t know the four-digit code, you cannot open the door. Of course, this doorlock can- not prevent the door being broken open, just as a norm al lock cannot do so. The electronics for this codelock is based on an integrated circuit specially manufactured for this pur- pose: the LS 7220. The keyboard has ten keys for the digits 0... 9, four of which are used to key in the code; they are connected to pins 3 ... 6 of the IC. The rema...