EXFO FTB-500 (Window XP) - Manual (Page 402)

IEEE 488.2 and Specific Command Reference
394 FTB-500
IEEE 488.2 Required Commands
*STB?
Description With the *STB? query you can read the status
byte and Master Summary Status bit. See the
content of this register below.
Syntax *STB?
Parameter(s) None
Response Syntax
N.U.
RQS/
MSS
ESB MAV N.U. EAV N.U. N.U.
MSB LSB Status By te Register