Datasheet for the HCF4017, the CMOS decade counter and divider with ten decoded outputs, provided as a 380 KB PDF. It should list the pinout, clock, reset and enable behaviour, timing diagrams and supply limits. A technician refers to it when checking why a sequencer or LED chaser stops stepping, confirming clock input and reset levels with a probe, and identifying which output pin corresponds to each count. CD4017 and HEF4017 versions normally share the same pin arrangement.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.