You can select a part of the signal by holding the left mouse button pressed and moving the signal ruler across the signal with the mouse. A selected
part will be shown with inverted color
(black background). If you want to extend the selection to the beginning or to the end of the
signal, you can press Home or End keyboard keys during the selection.
If you select some part of a signal as explained above and press the right mouse button, you will
see the exact position and length of the selected signal part in the context menu. This can be
used to measure a part of a signal, for example the difference between two FFT peaks or the
duration of a signal part.