The settings on the Sweep tab, except Duration (s), are only available if the Sweep checkbox is selected.  When Mute is cleared sweeps run continuously until Mute is selected again.

Frequency 2 (Hz) - sets the end frequency of a sweep.  The lowest frequency available is 10Hz.  The upper frequency limit will depend on the soundboard.  Frequency can also be set as musical pitch where, for example, 2 is the second octave and G# is the note.

Duration (s) - the time (in seconds) taken to sweep from Frequency 1 (Hz) to Frequency 2 (Hz).  It also sets the duration when saving single frequency and tone burst wav files.

Log - the sweep progresses in logarithmic steps.

Lin - the sweep progresses in linear steps.

Bi-directional - the sweep progresses alternately from Frequency 1 (Hz) to Frequency 2 (Hz) then from Frequency 2 (Hz) to Frequency 1 (Hz).  This option is not available if the input Mute is unset.