Reconizing when a computer connects to a phone line.

[fredje1]

Hello all you good people:
I am looking for a schematic that will recognize when a computer connects to a phone line Weather I am on the Phone or when the line is open or not in use. I was wondering if there is a simple solution like detecting a fax ring or modem. :? When you have a fax machine it can distinguish between a voice and a fax. How do they do this? Maybe this is the approach that I must use. Any way any suggestions will be of great help. I already have an off hook led that lights every time a call is being received or the line is in use. and what I want to do is to have a blue light led to light when a fax or a computer comes on line on the same phone line. Thank You for any information. Have a Merry Christmas and a Happy New Year. fredje1@joimail.com

 

[ljcox]

You partly answered the question yourself.

In Australia, you can have a distinctive ring pattern to distinguish incoming Fax calls from voice calls. If there is no DR, then the Fax machines have to recognise each other.

The Fax machine at the sending end sends bursts of tone and waits for a response. If the call is answered by a Fax machine it responds and they exchange data to determine the speed and format that the machines can use (one may be less capable than the other, so they must communicate at the lower level).

I don't know how computer to computer communication would work, I assume it would be similar.