Modem command requirements
- Last UpdatedApr 24, 2025
- 2 minute read
A limited and universal set of Hayes commands is used on the modem default configuration to ensure that the system is compatible with a variety of different modems.
Typically, a modem should function correctly right from the box. If any changes are required to the modem’s setup, they should be configured and saved using the AT&W command. The only modem setup required is taken from the appropriate modem configuration.
The controls described in the table below are used when the modem is waiting for a connection.
|
Control |
Description |
|---|---|
|
+++ |
This places the modem into command mode. A typical configuration has a 1.5- second pause before and after issuing this command. The modem should have a guard time of no more than one second. |
|
ATE0 |
This places the modem into no-echo mode. |
|
AT&C1 |
This forces the modem to monitor the true state of Data Carrier Detect (DCD) from the field modem. |
|
AT&D2 |
This forces the modem to monitor the true state of Data Terminal Ready (DTR) from the field modem. |
|
ATH0 |
This forces the modem to go on-hook or hang-up the phone line. |
|
AT&W |
This causes the modem to save the current configuration in non-volatile memory. |
|
ATD |
This causes the modem to dial a telephone number and attempt to establish the connection with the field modem. |
If a connection cannot be established, an error is reported. Refer to Modem Row Edit: Commands tab for the last 16 responses. If the modem gets an unexpected response (the usual response is "connect" or "busy"), the modem is declared out-of-service, and the connection is declared offscan. If a connection is established, the system begins to poll the remote indefinitely.