User guide

Internetworking Primer A-47
Modems
Proper DTR Interpretation
The modem must interpret a toggle of the DTR signal as a command to drop any active call
and return to the stored settings. Most modems use the settings &d2 or &d3. Refer to your
modem documentation for the settings used with your modem.
Other Modem Settings
This section defines other settings that may be needed or desirable depending on your
modem. For these settings refer to your modem documentation.
Best error correction
Error correction can be negotiated between two modems to ensure a reliable data link. Error
correction standards include LAPM and MNP4. V.42 error correction will allow either
LAPM or MNP4 error correction to be negotiated.
Modems differ in the way they enable error correction. Refer to your modem
documentation for the settings used with your modem.
Timesaver If you plan to support ARA v1.0 clients we suggest that you disable MNP4
error correction. Other users will negotiate LAPM.
Best data compression
Data compression can be negotiated between two modems and will allow for greater data
throughput. Data compression standards include V.42 bis and MNP5.
Modems differ in the way they enable data compression. Refer to your modem
documentation for the settings used with your modem.
Answering calls
If a modem will be used to service incoming calls, it must be configured to answer the
phone after a specific number of rings.