Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Telephone Monitoring

Status
Not open for further replies.
Hi,

I want to monitor telephone calls made by users so i could track who made what calls...I created a circuit whereby each user must enter a pin before using the phone. This works good but i am using the dial tone from the CO for them to enter their pin so what i am really doing is sending those four digits that consists of their pin to the central office each time. Once their pin matches what is stored in memory, i display "pin ok" and a relay breaks the telphone line and then reconnects giving the user the option to dial a number since they hear a dial tone once again from the CO. If the pin is invalid the user must re-enter a valid pin when i trip the line.

How do i mimic a dial tone so the user can enter his/her pin and i wouldn't have to keep sending this information to the exchange each time because someone told me that i am dropping the resstance at the exchange each time i do that and i could cause damage to their equipment. Is this true?...Would a mimic tone solve this problem? I need to create a mimic tone for the users to enter their pin in any case. Any help on how to do this please.
 
Last edited:
I can't imagine how dropping the resistance (which is a normal telephone function) and sending the 4 digits to the exchange each time could damage the exchange.

I would suggest just keep doing it as you are, if it seems to work properly.
 
Well that is what i said to myself as well because it works fine to my knowledge. However, my lecturer who is my supervisor for this project wants me to mimic a dial tone to enter their user pins instead of using the tone from the central office each time...How to do this?...I'm searching for a chip that does that but is unsuccessfull thus far.
 
Tone generation

thanks i will take a look at it and try to understand how to implement it to generate the tones. If you understand it already please post it.

Regards.
 
I haven't used it but if, after reading the data sheet, you have specific questions about its operation, I will try to answer.

Edit: Here's a circuit that uses op amps to generate the tone:**broken link removed**.
 
Last edited:
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top