Cell Phone Controlled Door Latch

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Cell Phone Controlled Door Latch

Cell Phone Controlled Door Latch

I ve been reading a lot on how DTMF (Dual Tone Multi Frequency) tones work over the last couple of weeks. I m sure you ve noticed that when you press the keys on a standard telephone keypad, an audible beep is generated. These beeps are actually the combination of two distinct frequencies. For example, the tone you hear when you press the number 9 on a telephone, is actually a combination of a 1447 Hz and 852 Hz signal. In a telephone exchange, these signals are decoded by a computer which finally connects the dialer to the designated phone line. For example, the tone of 1447 Hz and 852 Hz will be decoded as binary 1001 . In this project, I have designed a simple DTMF decoder circuit which allows me to control appliances in my house from any place on Earth using a telephone.