本规程规定了在打印35 mm、16 mm和8 mm S型电影胶片时，用于启动打印机换光机构的场景切换凹口或提示点的尺寸和位置。（更常用的帧数提示方法见附录A.1）。尽管本规程规定了用于启动打印机照明机构的凹口或提示点，但胶片在任何时候都不应同时包含这两种装置。

This practice specifies the dimensions and location of a scene-change notch or cueing spot for actuating the printer light-change mechanism when printing 35-mm, 16-mm, and 8-mm type S motion-picture films. (See annex A. 1 for a frame-count cueing method which is more commonly utilized).Although this practice specifies a notch or a cueing spot for actuating the printer light mechanism, at no time should a film contain both.