Notice on the Quad trace format that one trace has a red outline box on the graph, and the trace number in the Instrument Settings Summary (on the left side of the sweep window) is outlined with a red rectangle. This is the active trace, and only one trace is active at a time. Any display or format selection is applied only to the active trace.
You can change the active trace in two ways:
• In the Measure menu, press the Active Trace submenu key to select the trace that you want to be active. After a selection, notice how the active trace indicator on the display has changed. For example, if the active trace changed from TR1 to TR3, then the red highlight box moved from the upper left quadrant to the lower left quadrant.
Not only does the graph get highlighted in red, but the Instrument Settings Summary legend on the left side of the sweep window also highlights the active trace. This becomes more important when you are trying to distinguish between active traces and other traces when they are all overlaid on one graph.
• Touching a trace area or touching the trace data in the Instrument Settings Summary causes that trace to become active.
Magnifying Glass
When Trace Format is Dual, Tri, or Quad, you can magnify the active trace by touching the magnifying glass symbol in the upper‑right corner of the active trace.
Touching the magnifying glass symbol of a magnified trace reduces the trace size to return the display to the selected trace format.
While a trace is magnified, you can still change the active trace selection by touching the trace data in the Instrument Settings Summary.
Moving a Marker
When Trace Format is Single, Dual, Tri, or Quad, touching a trace can affect a marker. After the trace is active, you can touch and hold a marker to make it active. You can then move that marker by dragging with your finger. Your touch point on the vertical red line of the active marker represents a location on the x‑axis, and this touch point may be anywhere on the y‑axis (along the vertical red line). You can also double‑tap (quickly) anywhere within the active trace window to bring the active marker to the x‑axis location of your touch point. For greater precision, you can maximize the trace (with the Magnifying Glass icon) before moving the marker.
When the Marker Menu is Not Displayed:
You cannot move a marker with the Arrow Keys or the rotary knob.
When the Marker Menu is Displayed:
You can then move the active marker by touch, by keypad entry, by Arrow Key, or by rotary knob.
in the upper‑right corner of the active trace. 
of a magnified trace reduces the trace size to return the display to the selected trace format.