What does the AT Modem Command do?

I have a Problem. I'm involved in a Windows CE Software Projec开发者_StackOverflow中文版t that runs for a couple of years and one small part of it is the possibility to communicate with a modem. But that is one part of the technology I have absolutely no knowledge about.

Can someone explain me what the following AT Comand does that is send to the modem?

ATDT9,011,00w01234567890

The number behind the "w" is not a real one for this post.

Thank you very much

twickl

It's the Hayes AT command set. Basically you're telling the modem to dial a number.

AT = Attention, DT = Tone Dial, , = Pause and w is an up to 30-second (from memory) wait for at least a one-second dial tone.

The digits will be dialled like in a normal telephone.

Whoa, havent seen those in a while:
AT - Attention
DT - Dial Tone
9 - send number 9
, - wait
011 - Dial 011,
, - wait
00 - Dial 00,
w - wait for dial tone
012345 - Dial rest of number

Looks to me as if you´re dialing into some sort of PBX and then issue commands to it.

They are called "Hayes AT commands", named after the company Hayes, a dominant supplier of modems in the early days of PCs. There's little point in documenting it here, it googles very well. Take the first hit. But do beware that it has been arbitrarily extended by other manufacturers. You'll need a manual for the odd-balls, especially configuration commands.