 Some early systems were mechanical, using a rotating deflection coil around the neck of the display tube, but the electronics needed to do this using a pair of stationary deflection coils were not particularly complex, and were in use in the early 1940s.The specialist Beta Scan Scope was used for precision approach radar systems.It displays two lines on the same display, the upper one (typically) displaying the vertical approach (the glideslope), and the lower one the horizontal approach.