Listing 1. Hello World (Dial Tone Output)

#!/usr/bin/env python

from GnuRadio import *

def build_graph ():
    sampling_freq = 32000
    ampl = 8192

    fg = gr_FlowGraph ()

    src0 = GrSigSourceS (
        sampling_freq, GR_SIN_WAVE, 350, ampl)

    src1 = GrSigSourceS (
        sampling_freq, GR_SIN_WAVE, 440, ampl)

    sink = GrAudioSinkS ()

    fg.connect (src0, sink)
    fg.connect (src1, sink)

    return fg

if __name__ == '__main__':
    fg = build_graph ()
    fg.start ()        # fork thread(s) and return
    raw_input ('Press Enter to quit: ')
    fg.stop ()