This is an abbreviated form of the AT command set as appears in a USR modem manual. Most of these commands will work with any modem. If you are using them in Hyperterminal then you must have AT in front of them (in the "Extra Settings" field it automatically includes AT). I have edited out the commands which are not commonly used.
| AT | Prefix for all commands. Use on its own to get OK |
| DT5556969 | Dial 555-6969 using tone dialling |
| DP5556969 | Dial 555-6969 using pulse dialling |
| DL | Dials the last dialled number |
| H | ATH hangs up |
| In | I0 displays 4 digit product code
I3 displays the product type
I4 displays the current modem settings
I5 displays the NVRAM settings
I6 (while connected)displays connection statistics
I7 displays the product configuration (also shows nationality of modem) |
| Ln | Controls speaker volume
L0= Very Low
L1=Low
L2=Medium
L3=High |
| Xn | Controls how many errors the modem will report
X0 Ignores most errors
X1 Ignores NO DIAL TONE, BUSY and NO ANSWER
X2 Ignores BUSY and NO ANSWER
X3 Ignores NO DIAL TONE
X4 Ignores RING |
| Z | Resets modem |
| &Bn | Sets modem's serial port rate
&B0 Port speed adjusts for connection rate
&B1 Fixed serial port rate
&B2 Fixed in ARQ mode variable in non-ARQ mode |
| &Cn | Controls Carrier Detect signal
&C0 carrier Detect Override
&C1 Normal carrier Detect operations |
| &Dn | Controls Data Terminal Ready (DTR) operations
&D0 DTR override
&D2 Normal DTR operations |
| &Fn | Loads a read-only factory profile
&F0 Generic Template
&F1 hardware flow control template
&F2 software flow control template |
| &Hn | Sets Transmit (TD) flow control
&H0 No flow control (not recommended)
&H1 Hardware flow control (CTS)
&H2 Software flow control (XON/XOFF)
&H3 Hardware AND Software flow control |
| &In | Sets receive (RD) software flow control
&I0 Software flow control disabled
&I1 XON/XOFF signals to the modem and remote systems
&I1 XON/XOFF signals to the modem only |
| &Kn | Enables/Disables Data Compression
&K0 Disables data compression (not recommended)
&K1 Auto Enable/Disable
&K2 Data compression enabled
&K3 MNP5 compression disabled |
| &Mn | Sets Error Control (ARQ)
&M0 Error control disabled
&M4 Auto Enable Disable ARQ
&M5 ARQ on |
| &Rn | Sets receive (RD) hardware flow control (RTS)
&R1 Modem ignores RTS
&R2 Received Data to computer only on RTS (default) |
| &Un | Sets floor connect speed, if the modem does not connect at this speed it hangs up
&U0 Disabled (default)
&U1 300bps
&U2 1200bps
&U3 2400bps
&U4 4800bps
&U5 7200bps
&U6 9600bps
&U7 12,000bps
&U8 14,400bps
&U9 16,800bps
&U10 19,200bps
&U11 21,600bps
&U12 24,000bps
&U13 26,400bps
&U14 28,800bps
&U15 31,200bps
&U16 33,600 bps |
| S10=n | Sets the duration in tenths of a second that the modem waits after loss of carrier signal before hanging up.
S10=7 Default
S10=255 Don't hang up if carrier is lost |
| S11=n | Sets the interval in milliseconds between tones when
dialling.
S11=50 Default |
| S25=n | Sets the duration in hundredths of a second that the modem waits after loss of DTR before hanging up.
S10=20 Default |
| S38=n | Sets an optional delay in seconds before a forced hang up and clearing of the Transmit buffer when DTR drops during an ARQ call
S38=0 Default |