Short 44 KB PDF covering the 4N32 and 4N33 optocouplers, two closely related members of the 4N family that use a Darlington phototransistor output for high current transfer ratio. Such parts appear where a weak input must switch a larger load across an isolation barrier. The sheet is useful for pinout, LED drive limits, saturation voltage and switching speed, which matter because Darlington outputs are slower than plain phototransistor types. Check speed requirements before substituting a different 4N number.
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.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.