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
Thu Apr 28 2016, 01:15 AM
We don't provide project reports. We try to help you do your project
Wed Apr 27 2016, 06:02 PM
abebe tigabu
help me by sending final thesis project automatoc green house effect control by arduino or by at89c51 microcontroller
Mon Apr 25 2016, 03:40 AM
abhinav kumar
Hey there, i want to project report on the RFID BASED SECURITY SYSTEM using AVR microcontroler.please mail as soon as possible. Thank you
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i want c code for rfid based car parking system using 8051 and parking slot indicator.if u have please email me
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i need to work on OCR for Numbers, could not find any such projects done using 8051
Wed Apr 13 2016, 07:27 PM
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hey i am new to embedded system and i want to pursue ms in embedded, i have 2 years before i can apply for ms.. in two years can i gain sufficient knowledge. i know c and c++
ExperimenterUK
Wed Apr 13 2016, 05:15 PM
@Suraj.. the method will work ,but edit to suit your compiler
Wed Apr 13 2016, 01:05 AM
Suraj Sridhar
Can I use the LCD Device driver code for STM32F401RET6?
Mon Apr 11 2016, 04:38 PM
Ankith
Can I get the code to access the file from 8051
Mon Apr 11 2016, 04:37 PM
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can I access a file or folder from sdcard using 8051 microcontroller?

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