The silent witness dvr is exactly what it says your personal silent accurate witness to any incident you may be unlucky enough to encounter the sw001 is an entry level front facing dvr and crash cam which can be mounted on the windcreen in much the same way you mount your sat nav the sw001 has something called a g sensor crash file which holds a small file to record approximately 20 seconds of audio before and after the incident and approximately 10 seconds of video the footage taken is stamp