Profiles For Modems With External Switches; Modem And Scs Interaction; Initialization; Outgoing Calls - Lantronix SCS Reference Manual

Modems

9.3.4 Profiles for Modems with External Switches

Some modems, such as USRobotics Sportster and Courier, have external switches that control the modem's
behavior. Modems that have external switches but do not have predefined modem profiles on the SCS
should be set not to autoanswer. The SCS answers the phone; the modem should never pick up the phone
on its own.
Sometimes the switch settings can be overridden by command strings, but sometimes they cannot. If your
modem has switches, the SCS will tell you how to set the switches when you define the modem profile, as
seen in Figure 9-8.
Local>> DEFINE PORT 3 MODEM TYPE 30
%Info: Switch settings 1-8: UUDU DUUD
%Info: Port speed changed to 115200.
%Info: Port flow control changed to CTS.
In the example, "U" stands for up and "D" stands for down. Duplicate these settings on your modem, then
power cycle the modem before logging out of the port or rebooting the SCS.

9.4 Modem and SCS Interaction

9.4.1 Initialization

When the SCS is booted, the DTR signal will be held low so that the modem will reset and will not answer
incoming calls. All SCS ports with Modem Control enabled will be checked to see if a modem is connected
and powered up. To determine this, the SCS will send the Attention string to the modem and wait for the
OK string to be sent in response.
The modem will then be asked for its current configuration. The Init string will be sent followed by a request
for the modem's configuration. If the current modem profile on that port does not match the configuration
sent from the modem, it will be assumed that the modem's setup has changed. The Save string will be sent,
and the setup contained in the profile will be saved in the modem's permanent memory (NVR).
The NVR on some modems will wear out with repeated use. This limitation is
Note:
avoided by only writing the setup to the modem if it has changed.
The SCS will raise DTR so that the modem will answer incoming calls. The port then waits to start an
outgoing call and waits to receive the Ring string from the modem to start an incoming call.

9.4.2 Outgoing Calls

On outgoing calls, the SCS will send the Attention string until the modem responds with the OK string (up
to three times). If the modem does not send the OK string, the attempt will fail and the modem will be reset.
If the OK string is received, the SCS will send the Command Prefix, the Dial String, and the telephone
number to the modem.
To set the telephone number, refer to Assign a Telephone Number to the Port or
Note:
Site on page 4-19.
Figure 9-8: Enabling Modem Compression
9-8
Modem and SCS Interaction