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.

Get Social

Information

Powered by e107 Forum System

Conversation

hiast
Thu Jun 16 2016, 03:03 PM
help please how do i initiate port 3 as an input port in assembly? acutely there is push switch connecting to p3.2 push switch connecting to p3. 3 push switch connecting to p3.4 push switch connecting to p3.5 and i need to call function when the user pressed the push switch for the previous pins (not used as counter and not as timer… just call a function ( do special thing) when any push switch is pressed ???????
Mon Jun 06 2016, 12:02 PM
nida hussain
hi.. i need some help with keypad interfacing code.like i want to write a code in c language that takes an input of 2 digit numbers from a keypad interfaced with 8051 mc and stores the entered values in some array
Sat May 28 2016, 04:34 PM
kibrom berhe
c code for locker security system based on rfid and gsm
ExperimenterUK
Wed May 25 2016, 05:05 AM
@ Ramanjaneyulu, post in forum,explain your problem
Mon May 23 2016, 11:34 PM
Ramanjaneyulu
Hi, I Am using at89c4051 for my application, I want 5u sec dely.. Up to 1milli sec iam able to producing delay. Beyond the 1milli second, I am unable to produce the acceurate dely. Plz any one help me
Sat May 21 2016, 09:51 PM
A K
i want to mak an auto dialer using gsm and atmega 16. please helpe me how to write a code to auto dial a number saved in sim
Sat May 21 2016, 10:42 AM
Alec
Hi im trying to program my 89s51 with a usbasp so any ideas on the circuit?
Wed May 18 2016, 10:08 AM
Tashu joshi
anyone know how to develop
Wed May 18 2016, 10:07 AM
Tashu joshi
i'm working for resporatry system using 8051,
Wed May 18 2016, 10:06 AM
Tashu joshi
i'm developing a respiratory system using Arduino

Downloads

Comments

sung7333
Tue Jun 28 2016, 06:23 AM
Bonolai
Fri Jun 24 2016, 06:02 AM
hiast
Sat Jun 11 2016, 02:30 PM
alex1311
Thu Jun 09 2016, 06:57 AM
zaft93
Sun May 15 2016, 01:52 AM
CELEBI
Thu May 12 2016, 08:28 AM
Suro1996
Wed May 11 2016, 06:07 PM
yigithan
Sat May 07 2016, 09:09 PM

Online

Guests: 54, Members: 0 ...

most ever online: 182184
(Members: , Guests: 182184) on 06 Aug 2010: 05:37 AM

Members: 37769
Newest member: sung7333
Forum Activity
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed Jun 22 2016, 07:54 PM
I can't see why it should work sometimes and not o...
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed Jun 22 2016, 12:58 AM
You could use T0 and T1 to trigger interrupts but ...
Karan123 Avatar
Posted By Karan123
Tue Jun 21 2016, 04:40 AM
I am not Getting you . the project is to interfac...
Karan123 Avatar
Posted By Karan123
Tue Jun 21 2016, 04:34 AM
Hello,Thanks , It Works . Master-Slave address Ma...
alex1311 Avatar
Posted By alex1311
Mon Jun 20 2016, 11:38 AM
Football is my passion and I have dreamt of becomi...
ExperimenterUK Avatar
Posted By ExperimenterUK
Fri Jun 17 2016, 11:00 PM
>But Can't modify code at Receiver End for Differe...
hiast Avatar
Posted By hiast
Fri Jun 17 2016, 03:25 PM
thanks for help,i wanted to write this code as you...
Karan123 Avatar
Posted By Karan123
Fri Jun 17 2016, 12:19 PM
I don't your applications . But below should help ...
Karan123 Avatar
Posted By Karan123
Fri Jun 17 2016, 12:07 PM
I know i have to use below code at Transmitter End...
hiast Avatar
Posted By hiast
Thu Jun 16 2016, 02:58 PM
help pleasehow do i initiate port 3 as an input po...