Tektronix TBS1000C Series

Trigger slope and level concepts
The oscilloscope must detect both the slope and level conditions before it can
trigger and display a stable waveform.
The minimum trigger conditions needed to display a stable waveform are the
signal slope and threshold level. The slope sets the oscilloscope to find the trigger
point on the rising or the falling edge of a signal. The level sets where on that
edge the trigger point occurs.
The trigger Slope sets the oscilloscope to find the trigger event on the rising or
the falling edge of a signal.
The trigger threshold Level (or just level) is the signal amplitude value on a slope
that must occur for the oscilloscope to trigger on a signal.
Sampling oscilloscope concepts
40 TBS1000C Series Oscilloscopes User Manual