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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ExperimenterUK
Mon May 25 2015, 06:21 PM
@Subrat Sahu not a simple answer.Create a thread in "General help Guidance and Discussion" forum
Sun May 24 2015, 06:51 AM
Subrat Sahu
I have a confusion about 10 bit adc formula as describe bellow that resolution = Vref/1023 or Vref / 1024
ExperimenterUK
Sat May 23 2015, 08:54 PM
@utpal.. Create a thread in the Pic forum
Thu May 21 2015, 01:04 AM
utpal
i am a hobbist. i work on 8051. just i have started with pic 16f877. but a bitter experiance is going on. as i am programming any code to my pic877 and putting it in my board and it is working, but the 2nd time it is not taking any program,I have experimented just 7 new one pic mcus. result is the same. please tell me the reason. my programmer is TOP3000(universal programmer).
ajay_bhargav
Wed May 20 2015, 04:48 AM
@lak you can use the same code provided you are not using any s52 specific ports and registers.
Mon May 18 2015, 05:58 AM
lak
i used to develop a code for at89s52 shall i use the same code for at89c4051
Sun May 17 2015, 07:57 AM
Ayoosh
what if i have to rotate motor continuously at a step angle of 1.8 degree
ExperimenterUK
Fri May 15 2015, 06:02 PM
@oracle1946.. Post your question in the PIC forum
Fri May 15 2015, 03:48 AM
nadeem232
if some has solution kindly share solution Principles of Electric Circuits,by Thomas L. Floyd
oracle1946
Thu May 14 2015, 03:39 PM
I want to build a PIC16F684 sun logger using either a solar cell (0.5v solar cell or photoresistor). Any help out there?

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ExperimenterUK Avatar
Posted By ExperimenterUK
Mon May 25 2015, 06:16 PM
We need to do some simple tests.Get the speaker to...
mayank058 Avatar
Posted By mayank058
Mon May 25 2015, 04:57 AM
Dear sir, I am taking output from PI...
MuhammadTanvir Avatar
Posted By MuhammadTanvir
Sun May 24 2015, 11:11 AM
Hey guys !! Can somebody please share the proteus ...
ExperimenterUK Avatar
Posted By ExperimenterUK
Sat May 23 2015, 09:52 PM
Does the speaker work?.'Exactly' where on the boa...
ExperimenterUK Avatar
Posted By ExperimenterUK
Sat May 23 2015, 09:44 PM
For all your questions there is a proper, very tec...
mayank058 Avatar
Posted By mayank058
Thu May 21 2015, 04:46 AM
dear sir there is nothing to zip.I just...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed May 20 2015, 04:57 AM
can you zip your complete project and attach it he...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed May 20 2015, 04:46 AM
If you know how to drive 7-seg using an 8-bit port...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed May 20 2015, 04:42 AM
There was no proteus file included in the package,...
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Posted By ankitbajaj01
Tue May 19 2015, 07:00 AM
Hello ExperimenterUK...Please guide me on above po...