Discussion in "Electronics" started by    har    Nov 9, 2007.
Fri Nov 09 2007, 07:30 AM
#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, 09:20 AM
#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, 06:55 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, 09:15 AM
#4
a ring detector circuit.. might help you

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ajay_bhargav
Sat Aug 30 2014, 12:15 PM
@sufiyan, You can use solenoid lock in place of LED.
Fri Aug 29 2014, 12:17 AM
sufiyan
please can you tell me which type of lock activator should i connect in place of LED? can i use selenoid lock actuator
ajay_bhargav
Thu Aug 28 2014, 06:34 AM
Please post questions in forum
Thu Aug 28 2014, 01:44 AM
yednekachew
can you give a project made bay proteus software
Mon Aug 25 2014, 07:12 AM
Vinod Soni
Hi Sir, How can i make this RFID with ATMega16/32 controller
pavanjain
Sat Aug 23 2014, 05:10 AM
Sir i want to download the hex file in P89v51rd2 microcontroller using max232 IC but we not load the program in IC
Tue Aug 19 2014, 04:51 PM
allen ndumu
please i will like to know if the problem of speed control of dc motor using keypad and l298 was if yes can i have the complete project send it to the address i really need to see it
Tue Aug 19 2014, 10:47 AM
Amit Bisht
sir i want to have some trending projects on which i could work related to ATmega 16 microcontroller
ExperimenterUK
Sat Aug 16 2014, 04:16 PM
@diligent . create a thread
Sat Aug 16 2014, 03:17 PM
diligent
in assembly langauage programming..

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ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Sep 01 2014, 07:28 AM
Which RFID module are you using? Post link to the ...
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Posted By ajay_bhargav
Mon Sep 01 2014, 07:28 AM
We prefer to use English language on our forums. B...
bobparihar Avatar
Posted By bobparihar
Mon Sep 01 2014, 06:33 AM
i am using a RFID module, i want to connect reader...
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Posted By ajay_bhargav
Sat Aug 30 2014, 12:03 PM
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Sat Aug 30 2014, 11:56 AM
I found a very good working source but its for PIC...
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Posted By siddique
Sat Aug 30 2014, 03:34 AM
Have you tried using the TX setup to receive and v...
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Posted By ExperimenterUK
Thu Aug 28 2014, 03:31 PM
So, I don't think there is any need to load any da...
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Posted By ajay_bhargav
Thu Aug 28 2014, 06:33 AM
Did your professor ask this question to you? I sug...