Texas Instruments TI-73 Software Manual page 23

Communication Error
This error indicates that the TI™ Connect software ("Unable to
communicate with device") or TI-GRAPH LINK™ software ("Link
Transmission Error") is unable to communicate with the device.
The problem is usually associated with the TI-GRAPH LINK
cable and its connection to the device or to the computer.
• Make sure the cable is firmly inserted in the device link port
and the computer.
• Verify that the correct cable type is selected in the software
link settings.
• Verify that the correct communications port (Com Port) is
selected in the software link settings. (This does not apply if
you use the USB port and TI Connect software.)
TI-73 / TI-83 Plus Math by Hand Application Page 23