R F Cueing (Radio Frequency Cueing)

R.F.Cues are self-adhesive metal foil tabs stuck on the film between the perforations and the film edge a fixed number of frames from the scene change. The tabs are detected by a metal detecting probe as they reflect a radio frequency emission. The signal produced is used to activate the light change mechanism.

The advantage of this system, which was devised about 1969 and is still in use in laboratories today, is that no notches are cut, but the early versions, in particular had several disadvantages. The most serious is that sometimes the cue tabs fall off or even move! Secondly the adhesives were originally similar to clear adhesive tapes and solvent cleaning cleaned them off! After many years, these tabs pop off as either the adhesive dries or the adhesive becomes sticky and oozes out to stick onto other parts of the film. Cue tabs are unpredictable and many early films from about 1970 can still be printed using the original cue tabs as cues.