A device is described for the repeated mechanical scanning of a very short section of magnetic recording tape. The tape section, in a shuttle‐like holder, is moved backwards and forwards in front of a play‐back head. To obtain a constant speed movement, the tape holder is made to follow the contour of a cardioid curve section cut along the periphery of a rotating disk. The length of the scanning stroke is determined by the depth of the cut. A synchronizing contact is provided so that by triggering and adjusting the sweep of a cathode‐ray oscilloscope a stationary display may be presented on the screen. Typical applications are described.