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Possible reasons:
e Poor line quality
You have certainly experienced this on the normal telephone.
Another conversation barges in and interrupts your own
conversation. If you are calling over a satellite connection, you
may well experience echo and general interference.
If you have come in on a bad line, then break off and try again.
The transmission route between yourself and the remote modem
rarely follows the same route twice. A new attempt may well
produce a better connection.
Another alternative is to reduce
the transmission speed, at which rate the modem
is much less
sensitive to interference on the line.
Sometimes it is just not possible to achieve such a satisfactory
connection that data transfer is at all possible. Fortunately this is
a rare occurrence within national boundaries.
¢ Communication standard
The modem/communication program assumes another standard
than that which you have used. If the results obtained with 8 bits,
and no parity are worthless, then try with 7 bits, parity and one
stop bit.
Note that if you call at a transmission rate of 300 bps then the
other modem
must also be operating at the same rate. If you use
ITU-T communication standards and the other modem uses Bell
standard, then it will be impossible to obtain the CONNECT
message. It can happen, however, that a successful connection
between ITU-T and Bell may be achieved at the 1200 bps rate.
¢ Program
Occasionally the system at the remote modem uses special
techniques for representation of sound and picture. IBM-
compatible PCs frequently use, for example, ANSI Escape
codes. If your machine is not set up to be able to receive these,
the result will be gibberish on the screen.
LZTR104006 R1.00
2-17
Zat 14.4/14.4-7 and Zat 19.2/19.2-7
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