AT Commands For Dial-up Modems
| Field | Computer modem operation |
| Went Obsolete | DSL/Cable modem saturation, still in use for cell-network data links |
| Made Obsolete By | DSL/Cable modem affordability |
| Knowledge Assumed | Modem operation |
| When useful | If you find yourself with a modem on an OS without a normal PPP program, or troubleshooting a cell-network data link |
AT commands were used to operate modems, to put it simply. You used a terminal program to issue AT commands to the modem and operate it. For example, ATZ was the usual command to “soft” reset a modem, while ATDT [no.] was used to dial a given nuber with tone dialing. The usual interaction, the simplest one, would go like this:
“ATZ”
“OK”
“ATDT 55566677”
Before soft modems became the norm, modems usually came with a booklet that describe the AT commands supported by the device.
Note: This skill can still be useful when using cellphone with GPRS/CDMA/3G technology to access the internet. These phones acts as a high speed dial up modem. For most phone model, in most Operating System (including Windows), you will need to know the AT command to setup the APN (Access Point Name) and/or connection mode. Also still used for some classes of fax operation.
