Information Technology Reference
In-Depth Information
Figure 15.6
Example modem settings
15.6 Modem indicator
Most external modems have status indicators to inform the user of the current status of a con-
nection. Typically, the indicator lights are:
•
AA - is ON when the modem is ready to receive calls automatically. It flashes when a
call is incoming. If it is OFF then it will not receive incoming calls. Note that if the S0
register is loaded with any other value than 0 then the modem goes into auto-answer
mode. The value stored in the S0 register determines the number of rings before the mo-
dem answers.
•
CD - is ON when the modem detects the remote modem's carrier, else it is OFF.
•
OH - is ON when the modem is on-hook, else it is OFF.
•
RD - flashes when the modem is receiving data or is getting a command from the com-
puter.
•
SD - flashes when the modem is sending data.
•
TR - shows that the DTR line is active (i.e. the computer is ready to transmit or receive
data).
•
MR - shows that the modem is powered up.
15.7 Profile viewing
The settings of the modem can be determined by using the AT command with &V. An ex-
ample is shown next (which uses a program from Chapter 13). In this it can be seen that the
settings include: B0 (CCITT 300 or 1200 bps for call establishment), E1 (enable command
