Verilink Productivity 500 (34-00236) Product Manual - Manual (Page 81)

Troubleshooting Guide 500 TA Page 81
• You may need a different type of PC cable. If your PC port is set up as a
DCE, then you may need a crossover (null modem) cable, which reverses the
receive and transmit lines. Try to find out the function of the pins on PC's
serial interface port, and compare them with the unit's pin functions listed in
Appendix E . For example, the PC's receive pin should be connected to the
unit's transmit pin, and vice versa.
• Some PCs expect a CD and CTS signal from the 500 TA in order to transmit.
In the default configuration, both CD and CTS are forced (always on).
If the TD LED blinks when the unit receives an AT command, but the RD LED
does not blink (indicating the 500 TA does not respond to the command), then
the problem may be in either the PC's configuration or the unit configuration.
• Make sure the 500 TA is set to the proper communications mode. The 500
TA will only respond to AT commands if it is in the command mode.
• Make sure the unit's AT command interpreter is enabled. Try unplugging and
plugging the power supply to cause the 500 TA to reset. The Installation
chapter describes how to force the 500 TA into AT command mode.
• Be sure that the PC either provides a DTR signal, or that the 500 TA is set to
force DTR On (DTR Option 0, AT&D).
AT commands echoed from the 500 TA are not displayed correctly at the
PC (but response messages are).
• Check the PC echo option. If the PC displays duplicate characters (i.e.
AATT), PC echo should be disabled. If the PC does not display AT at all, be
sure PC echo is enabled.
AT response messages are not being displayed properly at the PC (but AT
commands are).
• First, be sure that the unit's AT command interpreter is enabled and that AT
messages are enabled. Both these settings are the default. The Installation
chapter describes how to force the 500 TA into AT command mode.
• If numbers are being returned from the 500 TA when you enter commands,
the 500 TA is probably set to return message codes instead of messages.
Change to the message code option.
• Some terminals automatically display what is typed, rather than waiting for
the 500 TA to echo the characters (half-duplex mode). It is possible that the
AT commands aren't really getting to the 500 TA at all, but are being dis-
played on the terminal anyway. If the AT commands are getting to the 500
TA, it's TD LED will blink.