ADLINK PXI-2208 - Manual (Page 87)

Operation Theory 75
Figure 4-35: High-Hysteresis Analog Trigger Condition
Low-Hysteresis Analog Trigger Condition
Figure 4-36 shows the low-hysteresis analog trigger condition,
the trigger signal is generated when the input analog signal
level is less than the Low_Threshold voltage, and the
High_Threshold voltage determines the hysteresis duration.
Note the High_Threshold setting should be always higher then
the Low_Threshold voltage setting.
Figure 4-36: Low-Hysteresis Analog Trigger Condition