Tektronix TPS2000 Series User Manual page 216

Reference
Coupling. Coupling allows you to filter the trigger signal used to
trigger an acquisition.
Option
DC
Noise Reject
HF Reject
LF Reject
AC
NOTE. Trigger coupling affects only the signal passed to the trigger
system. It does not affect the bandwidth or coupling of the signal
displayed on the screen.
Pretrigger. The trigger position is typically set at the horizontal center
of the screen. In this case, you are able to view five divisions of
pretrigger information. Adjusting the Horizontal Position of the
waveform allows you to see more or less pretrigger information.
9- 40
Details
Passes all components of the signal
Adds hysteresis to the trigger circuitry; this reduces sensitivity
which reduces the chance of falsely triggering on noise
Attenuates the high-frequency components above 80 kHz
Blocks the DC component and attenuates the low-frequency
components below 300 kHz
Blocks DC components and attenuates signals below 10 Hz
TPS2000 Series Digital Oscilloscope User Manual