How-to
Samples must be:
Samplerate: 8000Hz
Bitrate: 8 bit unsigned integer
Duration: 5 seconds
Channels: 1 (mono)
In audacity: File->export->other uncompressed formats: WAV, codec: Unsigned 8 bit PCM.
Software
Audio Editor: audacity
U-load software: u-load
Windows Driver:
zadig