TS555 Timer

  
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How the circuit works is simple when you send a DTMF tone to the decoder the value of pin 15 goes high for a short time this makes an excellent trigger as it supplies a few volts to pin 2 of the 555 Timer this triggers the circuit and turned the relay on for a short time. If you want different times you can experiment with R1 use a Potentiometer or a preset one. 3). Now as soon as Pin 2
TS555 Timer - schematic

on the 555 Timer has a few volts at the Trigger input of pin 2 this will switch the relay over for about 5 seconds if you have set one touch dial or speed dial on your Modified Cell phone then this will call you letting you know it has received valid DTMF tones. 4). It would be best to have this go to a mobile phone if you are still connected to the DTMF Decoder then it would be best to turn your Answer phone off before you make the call to the DTMF Decoder as the sending back phone will call what number is locked in it`s memory. 5). Now most Cell phones have a time delay of 2 or 3 seconds when touch or speed dial is activated this simple design gives you 5 seconds then it switches back waiting for the next time you connect to the DTMF Devise to activate it again. 6). The design is simple to follow it would be a good idea if you set on the transmitting phone the Auto Re-dial you have to turn your answer phone off on your receiving phone just in case it went to answer phone. 7). Now setting the Auto Redial on the sending back mobile phone is good as if you did not disconnect in time it will just phone your again then you just disconnect the incoming call as it has showed on your Screen what call is coming in. 8). In this design I have used a back up Modified cell phone for the Re-sending of the notification signal to me the incoming call does not need to be answered just disconnect the incoming call and you will not be...



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