This section presents the Dial Tone example implemented using the GNURadio plat
form. This example produces an audio sound composed by two cosine signal sources and
by a noise signal source. The output is converted to an audio format using the audio sink
block, allowing the signal to be heard. Figure 3.1 shows the schematic for this example,
on the GRC. First, the Signal Source block creates cosine waves; the frequency is adjusted
using a WX GUI Slider, a variable slider that ranges from 0 to 1000; the amplitude of the
wave is set to 0.1. There are two Signal Sources: one with the default frequency of 350
Hz and another with 450 Hz. The Noise Source block creates a Gaussian noise; this block
also has a WX GUI Slider associated with the noise amplitude that ranges from 0 to 0.1