
| 
 | 
 | Chapter 4 - AT Commands,  | 
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| Command: | Bn | Communication Standard Setting | 
| Values: | 
 | n =  | 
| Default: | 
 | 1 and 16 | 
| Description: | B0 | Select  | 
| 
 | B1 | Select Bell 212A when modem is at 1200 bps. | 
| 
 | B2 | Deselect V.23 reverse channel (same as B3). | 
| 
 | B3 | Deselect V.23 reverse channel (same as B2). | 
| 
 | B15 | Select V.21 when the modem is at 300 bps. | 
| 
 | B16 | Select Bell 103J when the modem is at 300 bps. | 
| Command: | Cn | Carrier Control | 
| Values: | 
 | n = 1 | 
| Default: | 
 | 1 | 
| Description: | C0 | Transmit carrier always off. (Not supported.) | 
| 
 | C1 | Normal transmit carrier switching (included for backward compatibility with some software). | 
| Command: | Ds | Dial | 
| Values: | 
 | s = dial string (phone number and dial modifiers) | 
| Default: | 
 | none | 
| Description: | 
 | Dial telephone number s, where s may up to 40 characters long and include the  | 
| 
 | 
 | and D characters, and the L, P, T, V, W, S, comma (,), semicolon (;), !, @, ^ and $ dial string | 
| 
 | 
 | modifiers. | 
Dial string modifiers:
LRedial last number. (Must be placed immediately after ATD.) P 
T 
V Switch to speakerphone mode and dial the following number. Use ATH command to hang up. W Wait for a new dial tone before continuing to dial. (X2, X4, X5, X6, or X7 must be selected.)
, Pause during dialing for time set in register S8.
; Return to command mode after dialing. (Place at end of dial string.)
! Hook flash. Causes the modem to go 
@ Wait for quiet answer. Causes modem to wait for a ringback, then 5 seconds of silence, before processing next part of command. If silence is not detected, the modem returns a NO ANSWER code.
^ Disable data calling tone transmission.
$ Detect AT&T call card “bong” tone. The character should follow the phone number and precede the user’s call card number: ATDT1028807637853500$123456789
| Command: | DS=y | Dial Stored Telephone Number | 
| Values: | 
 | y =  | 
| Default: | 
 | none | 
| Description: | 
 | Dial a number previously stored in directory number y by the &Zy=x command. | 
| 
 | 
 | Example: ATDS=3 | 
| Command: | En | Echo Command Mode Characters | 
| Values: | 
 | n = 0 or 1 | 
| Default: | 
 | 1 | 
| Description: | E0 | Do not echo keyboard input to the terminal. | 
| 
 | E1 | Do echo keyboard input to the terminal. | 
| Command: | Fn | Echo Online Data Characters | 
| Values: | 
 | n = 1 | 
| Default: | 
 | 1 | 
| Description: | F0 | Enable online data character echo. (Not supported.) | 
| 
 | F1 | Disable online data character echo (included for backward compatibility with some software). | 
| Command: | Hn | Hook Control | 
| Values: | 
 | n = 0 or 1 | 
| Default: | 
 | 0 | 
| Description: | H0 | Go  | 
| 
 | H1 | Go  | 
| MT4X56USB | 41 |