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when operating with poor line quality.
If the telephone line drops out, MNP 10 will attempt to reconnect up to the maximum time
permitted by your country’s telecommunications rules. Thus, if there is a short line drop-out,
MNP 10 will provide minimal interruption whereas other modems will disconnect entirely.
MNP is the only type of error correction allowed with MNP 10 and is only available when
connected to another modem that supports MNP 10. The #K command is used to select MNP
10.
Speed Changes
Although MNP 10 is able to cope with bad telephone connections, your modem must be able to
first make a connection with another modem before it can make use of MNP 10. For this reason
you may wish to use the AT%H1 command to force your modem to connect at 1200 bps and
then ‘upshift’. Most telephone lines will cope with V.32 or V.32bis connections, however
connecting at 1200 bps will ensure you make a connection. You may also use the J dial modifier
to force your modem to make the initial MNP 10 connection at 1200 bps.
When MNP 10 changes line speed (either up or down) there will be a slight interruption to your
communications. For this reason you should always use flow control to ensure data is not lost
when MNP 10 changes line speed.
If you wish to establish the connection prior to MNP 10 upshifting or downshifting, issue the
%H9 command. This allows you to use the connection before MNP 10 attempts to change the
connection speed.
Cellular Modem Users
If you are making modem calls with a cellular phone, issue the AT#K2 command. This tells
MNP 10 to try even harder to maintain the connection if your cellular call momentarily drops
out.
With such a choice, you may be wondering which combination you should be using. The table
below shows the relative performance of each combination of error connection and data
compression.
If you are connecting to various makes and models of modems, V.42/V.42bis auto-reliable mode
is probably the best alternative (AT\N3%C2). V.42/ V.42bis auto-reliable mode will also connect
to another modem that supports MNP with V.42bis data compression. For overseas or cellular
connections, use MNP 10 if possible (AT\N3%C2#K1).