Discussion in "Electronics" started by    har    Nov 9, 2007.
Fri Nov 09 2007, 12:30 PM
#1
thanks for the reply

actually sir i wanted to do an project on security system with auto dial up circuit which plays the recorded message via telephone. hence i wanted the circuit details and telephone circuitory working fundamentals
regards
Fri Nov 09 2007, 02:20 PM
#2
there is a project using telephone interface in the download section.. take the circuit as reference.. and please do not create duplicate topics
Voice Ineractive System For College Automation project
Sat Nov 10 2007, 11:55 PM
#3
JUST TO REFER HOW TELEPHONE WORKS REFER THIS LINK
http://communication.howstuffworks.com/telephone.htm/printable
and this may also help as add on
This recorder can be connected to the telephone lines just about any place, and no external power source is needed. The tape recorder's switch terminals are applied to a pair of transistors, connected as Darlingtons, that are used to turn the recorder on and off. When the telephone is off-hook there's usually about 50 Vdc across the phone thats divided over R1, R2, and R4, so that Q1's base is negative enough to keep the recorder off. Pick up the receiver, and the voltage drops to 5 V. That leaves not quite-enough voltage on Q1's base to keep that transistor at cutoff, so the recorder begins. Remember to keep your recorder's switch in the on position, and depending on how many people use the telephone, remember to rewind or change tapes occasionally!
Sun Nov 11 2007, 02:15 PM
#4
a ring detector circuit.. might help you
 har like this.

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Mon Feb 15 2016, 02:10 AM
salma
i would like to ask about this code can be used in fire detection devices or not
ExperimenterUK
Fri Feb 12 2016, 08:39 PM
@ Ankush SS .. source code for what?
plinniocom2n
Fri Feb 12 2016, 04:17 PM
thank you
Wed Feb 10 2016, 09:17 AM
Ankush SS
Can i get the source code of this project? Please n thnk u for ur kindness
Sat Feb 06 2016, 12:33 AM
SANJYOT JADHAV
sir did we have to use Gsm modem for testing the circuit on proteus
Wed Feb 03 2016, 03:17 AM
upendra kumar
i want information about 3-phase motor control using gsm technology
Sun Jan 17 2016, 09:33 AM
Kenneth Etuk
Hi everyone, I need help with a project involving MCU,rttc, and DC motor. I will pay for it. please reply to my mail [email protected] if you are interested. thanks
ExperimenterUK
Sat Jan 16 2016, 06:08 PM
@Kabona Log in and create a thread. Tell us what you want to do
Wed Jan 13 2016, 12:24 PM
Kabona
how can I make my pc be input and output device for the microcontroller
Sat Jan 09 2016, 11:04 PM
Ravz
Thank u..... one more doubt Will ultrasonic sensor HC-SR04 works with aurdino board in operating system linux

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Fri Feb 12 2016, 12:12 AM
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sankalp_s Avatar
Posted By sankalp_s
Sun Feb 14 2016, 08:02 PM
Try this program.Let me know if it makes sense to ...
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Posted By ExperimenterUK
Fri Feb 12 2016, 11:04 PM
Try this program.Let me know if it makes sense to ...
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Posted By ExperimenterUK
Fri Feb 12 2016, 04:45 AM
How do I get the link to the file? plinniocom2nGoo...
plinniocom2n Avatar
Posted By plinniocom2n
Fri Feb 12 2016, 12:18 AM
How do I get the link to the file? Newbie here.
sankalp_s Avatar
Posted By sankalp_s
Thu Feb 11 2016, 06:28 PM
Hello phil sir finaly i'm dumping my code, now i'm...
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Posted By ExperimenterUK
Thu Feb 04 2016, 04:10 AM
Sir I didn't understand that. Could you explain ab...
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Posted By sankalp_s
Tue Feb 02 2016, 07:26 PM
but good use of sub routines will save a lot of ...
ExperimenterUK Avatar
Posted By ExperimenterUK
Tue Feb 02 2016, 12:25 AM
after removing ALLON instruction it's working fine...
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Posted By ExperimenterUK
Tue Feb 02 2016, 12:14 AM
Which micro controller are you using ?.Does it hav...
sankalp_s Avatar
Posted By sankalp_s
Sat Jan 30 2016, 07:40 PM
You need to explain exactly what you want the code...