Marker coil at Fort Totten station
A marker coil, which is part of Metro's automatic train control system, in the trackbed at Fort Totten station in Washington, DC.
Ben Schumin is a professional photographer who captures the intricacies of daily life. This image may be used under Creative Commons Attribution-ShareAlike 2.0. Please provide artist attribution, as well as a link to the original photo and to the license terms.