The freq_generator takes values from it's in_signal input and
translates them into frequency and phase_step values.

When in_signal provides a signal below sig_range_lo, then freq_range_lo
is the frequency which will be output. Conversly, when in_signal's
value is above sig_range_hi, freq_range_hi will be the outputted
frequency.

The step_count parameter says there should be n number of divisions
between the two frequencies specified. If the two frequencies are an
octave apart, you might specify step_count as 12 so that the
frequencies output are those used by the western equal temperament
note scale.

out_phase_step outputs the frequency translated to a step value.

See also: osc_clock sine_wave note_tran
