Twin-lens reflex. A camera with two lenses, one for taking pictures and one for viewing the scene. The two lenses are typically linked to ensure that they remain focused at the same distance. Found on http://en.wikipedia.org/wiki/List_of_abbreviations_in_photography
Twin Lens Reflex camera. A fixed mirror replaces the SLR's flip-up mirror, so making this design very quiet. (Medium Format) 6cmx6cm. Rollei is the best known. (see Medium format, Parallax error & SLR )
Found on https://www.encyclo.co.uk/local/20176