<?xml version="1.0" encoding="ISO-8859-1"?>
<example id="dial_tone_ex"><title>Dial Tone Output</title>
<programlisting>
#!/usr/bin/env python

from gnuradio import gr
from gnuradio import audio

def build_graph ():
    sampling_freq = 48000
    ampl = 0.1

    fg = gr.flow_graph ()
    src0 = gr.sig_source_f (sampling_freq, gr.GR_SIN_WAVE, 350, ampl)
    src1 = gr.sig_source_f (sampling_freq, gr.GR_SIN_WAVE, 440, ampl)
    dst = audio.sink (sampling_freq)
    fg.connect ((src0, 0), (dst, 0))
    fg.connect ((src1, 0), (dst, 1))

    return fg

if __name__ == '__main__':
    fg = build_graph ()
    fg.start ()
    raw_input ('Press Enter to quit: ')
    fg.stop ()
</programlisting>
</example>