US Robotics COURIER User Manual page 148

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COURIER HIGH SPEED MODEMS
Both modems ...
Exchange carrier signals, but fail to establish a communications link
1.
If you have a fax modem, make sure it is in the correct mode,
fax or data, depending on whether the connection is to be
made with a facsimile device or a data modem. See
Fax
Operations in Appendix E for information on switching
between fax and data modes.
2. Asynchronous operations: Check to make sure the proper
bit rate, word length, parity and number of Stop bits have
been selected. Synchronous operations: review the link
instructions in Chapter 7. If you've set the modem to the
correct configuration, the problem may be with the
synchronous adapter or with the system you're trying to call.
3. Check to see that your modem is at the correct Bn setting to
connect with either an HST modem (Bl setting) or V.32
modem (BO setting). Type ATI4 for a display of the
Courier's current settings and, if necessary, send the modem
the correct setting.
4.
If your modem is attempting to answer a V.32 call, you may
need to lengthen the extra V.32 answer tones. See S28 in
Appendix 5.
5. Depending on your model, make sure the modem at the
other end of the line is HST compatible, V.32 bis compatible
at 14.4K bps, or V.32 compatible at 9600 bps, V.22 bis-
compatible at 2400 bps, Bell 212A-compatible at 1200 bps, or
Bell 103-compatible at 300 bps. These are the common
signaling standards for full duplex dial-up network
transmission in the U.S.
6. Make sure your modem's link rate setting, &Nn is correct for
the call. If the link rate is locked at a speed (&Nl-&N9)
different from the calling modem's, the Courier hangs up.
The factory setting of &NO, variable link operations, allows
the two modems to negotiate the highest possible link rate.
7. If none of the above corrects the problem, it's likely that the
quality of the phone connection is poor and that the other
modem is missing the signals your modem is transmitting.
The variable quality of phone line connections may be due to
any number of conditions in the phone service's equipment
Problems and Solutions D-3