Agilent Technologies E5071C ENA Service Manual page 296

Messages
execution of GPIB commands and others that indicate the internal status of the equipment.
Error messages are indicated following the character string "[Err]" and can be read out by a
GPIB command. Other kinds of messages are indicated without the "[Err]" character string
and cannot be read out by a GPIB command. This section explains the meaning of each
message and how to resolve the problem it indicates.
296 Appendix E