Tektronix 1A4 Instruction Manual page 158

Calibration—Type 1A4
If it is necessary to check the positions of the unchanged
controls, refer to the list that precedes step 25 with this
exception: DISPLAY switch should be set to CHOP.
c. Using the Type 1A4 POSITION controls, position Chan-
nel 1 segmented trace about 1.5cm above graticule center
and position the traces of the other channels in succession
about one cm apart below Channel 1 (see Fig. 7-33A}. Use
the oscilloscope Triggering Level control to obtain a display
similar to Fig. 7-33A or, if desired, trigger on any channel.
channels.
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