20 of an instrument the display includes a graphic display 21 and a tabular display 22 multiple traces are shown within graphic display 21 each trace is a waveform representing for example a laser line within an optical transmission system a scroll bar 23 can be used to scroll tabular display 21 within tabular display 22 a first column indicates a channel number for a single trace waveform a second column indicates a center wavelength for the waveform a third column indicates peak power for the waveform a forth column includes a bar that graphically represents power a scroll bar 24 is used to scroll tabular display 22 a cursor 26 is controlled by a pointing device such as a mouse or touchpad to select one of the center wavelengths listed in the second column for example a center wavelength is selected by a user placing cursor 26 over one of the center wavelengths listed in the second column of tabular display 22 and u201c clicking u201d a button on the pointing device in fig2 cursor 26 is shown selecting the center wavelength for the channel 1 wavelength in a block 12 of the flowchart shown in fig1 a check is made to ascertain whether the zoom feature is active within the example shown in fig2 the zoom feature.