Agilent Technologies ESA Series User's/Programmer's Reference page 213

NOTE All bits are summary bits from lower-level event registers. (For a general diagram
of the STATus:QUEStionable register, see
A Questionable Status condition register query response will be the decimal sum of the bits which are set
to 1. For example, if bit number 9 and bit number 3 are set to 1, the decimal sum of the 2 bits is 512 plus
8. So the decimal value 520 is returned.
The transition filter specifies which types of bit state changes in the condition register will set
corresponding bits in the event register. The changes may be positive (from 0 to 1) or negative (from 1 to
0). Send the command :STATus:QUEStionable:NTRansition <num> (negative transition) or
:STATus:QUEStionable:PTRansition <num> (positive transition) where <num> is the sum of
the decimal values of the bits you want to enable.
The Questionable Status event register latches transition events from the condition register as specified
by the transition filters. Event registers are destructive read-only. Reading data from an event register will
clear the content of that register. To query the event register, send the command
:STATus:QUEStionable[:EVENt]?
Chapter 4
Use Status Registers to Determine the State of Analyzer Events and Conditions
Figure 4-9.)
Status Registers
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