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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yogesh puri Avatar
Posted By yogesh puri
Thu May 25 2017, 10:33 PM
dear sirif i simulate the above program in keil it...
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed May 24 2017, 09:42 PM
If you run the display in 4 bit mode and share pin...
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed May 24 2017, 09:27 PM
Please post your code and Proteus file.
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed May 24 2017, 09:23 PM
i am unable to simulate following code in protous...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed May 24 2017, 05:01 AM
Duplicate post of http://www.8051projects.net/t651...
ajay_bhargav Avatar
Posted By ajay_bhargav
Wed May 24 2017, 05:00 AM
All I can say looking at the post is "insufficient...
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Posted By ajay_bhargav
Wed May 24 2017, 04:58 AM
(the 3 motorsteppers need to move independently, b...
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Posted By ajay_bhargav
Wed May 24 2017, 04:55 AM
I am never sure with Proteus keypad. They always h...
yogesh puri Avatar
Posted By yogesh puri
Tue May 23 2017, 10:36 PM
i am unable to simulate following code in protous....
yogesh puri Avatar
Posted By yogesh puri
Tue May 23 2017, 10:34 PM
i am unable to simulate following code in protous...