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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Posted By ExperimenterUK
Sat Jun 16 2018, 11:33 PM
hi sir sorry for the late reply sir can we control...
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Posted By LAMBO
Sat Jun 16 2018, 07:15 AM
hi sir sorry for the late reply sir can we control...
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Posted By ExperimenterUK
Mon May 14 2018, 10:17 PM
So the main problem is that I am not getting Analo...
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Posted By ExperimenterUK
Mon May 14 2018, 09:40 PM
Hi sir after checking all the connection i...
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Posted By LAMBO
Sun May 13 2018, 02:13 PM
Hi sir after checking all the connection i...
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Posted By ExperimenterUK
Mon May 07 2018, 07:27 PM
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Mon May 07 2018, 01:28 PM
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Thu May 03 2018, 03:32 PM
If the circuit works with a light bulb, the probl...
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Posted By LAMBO
Thu May 03 2018, 08:04 AM
Hi sir as u mentioned above everthing is working...