Source : Free On-Line Dictionary of Computing

voice-net
     
        Hackish way of referring to the {plain old telephone system},
        comparing it to a digital {network}.  {Usenet} {sig block}s
        sometimes include the sender's telephone number next to a
        "Voice:" or "Voice-Net:" header; variants of this are
        "Voicenet" and "V-Net".
     
        Compare {paper-net}, {snail-mail}.
     
        [{Jargon File}]
     
        (1995-02-16)