Tektronix 551 Dual Beam Instruction Manual page 12

ter of the graticule (for the beam on which triggering is oc­
curring. If you move the TRIGGERING LEVEL control towards
+ , the starting point will be raised, while if you move the
TRIGGERING LEVEL control towards —, the starting point
will be lowered. (Fig. 2-5).
The four comments at the close of the section on the AC
and AC LF REJECT triggering mode apply also to triggering
in the DC mode. The following statements can be made to
compare the DC with the AC and AC LF REJECT modes of
triggering:
1. When you use the DC mode, the trace always starts at a
given point on the graticule, for a given TRIGGERING LEVEL
setting, and the display must be positioned to pass through
this point. But when you use the AC or AC LF REJECT mode
of triggering, the trace always starts at a given point on the
waveform, for a given TRIGGERING LEVEL setting (regard­
less of the VERTICAL POSITION setting).
2. The DC mode is especially useful for viewing waveforms
which change slowly.
Fig. 2-5. In the DC triggering mode, the TRIGGERING LEVEL control
determines the point on the graticule at which the display will start.
Getting Acquainted— Type 551
2-5