Rekall Dynamics Professional IN USE SIGN. A professional In Use Light for Television, Radio, Music & Broadcast Studios. (Low Voltage: 12-24vDC) A Commercial In Use Sign Fitting designed to be almost indestructible in Challenging Environments, these are not a Cheap Replica, Reproduction or Movie Prop. A top of the line Metal and Polycarbonate Warning Light as used by hundreds of the worlds leading Recording Studios and Broadcast Facilities. SMD LED Ultra Bright Illumination with Integrated Internal Power Supply. Included accessory kit with mounting hardware and access tool. As used by Bose, Dolby, Pinewood, Film Roman, and even NASA and Facebook.