Message Waiting Light，Residential， IP， PBX &amp; Key System<div style="text-align: left;"><strong>[Product Information]</strong><br><ul><li>Detects; CLASS/FSK signal (message waiting visual feature).</li><li>IP，PBX and Key system that uses the message waiting visual Signal (CLASS/FSK Signal).</li><li>Line powered， no battries or transformers.</li><li>FCC approved.</li><li>This is the only unit manufactured that works with a residential/IP line.</li></ul></div><img src="http://ecx.images-amazon.com/images/I/317WLmpJrpL.jpg" noproxy>