INSYS Modem 336 LL 2D/4D 5.x Originate / Answer, Manual

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INSYS Modem 336 LL 2D/4D 5.x Originate / Answer Diagnosis and Testing of the Path
14 Diagnosis and Testing of the Path
14.1 Line Optimization
To query the line quality and the received signal level a connection must be established
between the two modems (
CONNECT ).
Use the Escape sequence “+++” (with > 1 second pause before and after the sequence) to
switch to the online command mode.
Activate the level with the command
AT%L . The displayed value in the scale -dBm is not
equivalent to the line level but the level within the data processor part of the modem.
The modem will be able to recognize a remote terminal up to the level value -40. The op-
timum values will be around 20.
The command
AT%Q queries the connection quality. Lower values indicate a better line
quality with a less significant error rate – for connections that have not been error-
corrected – and a higher data transfer rate for error-corrected connections.
The command
ATO terminates the online command mode.
14.2 Error Sources
If the modems don’t establish a connection all, the following reasons could apply:
 The two remote terminals were set to different connection protocols (V.xx,
to be set with
AT+MS=<n> ).

The two remote terminals are fixated on different error correction proto-
cols (None, MNP, V.42).
 a1/b1 and a2/b2 have not been connected crosswise during four wire op-
eration.

The transmit level is too strong or too weak (check with a level gauge or ad-
just the S registry (
ATS91
) on both sides).
 Strong interferences occur on the line (e.g. if the line is running parallel to
lines with high interference voltages).

The baud rate or the data format of the serial interface has been set incor-
rectly. Therefore the modem can not receive or send valid data.
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