Only the part number 2SC5423 appears in the name of this small 30.0 KB PDF. Following JIS rules, the 2SC prefix identifies an NPN bipolar transistor, so the content is presumably a short datasheet. Use it to look up pin assignment, maximum ratings and typical characteristics when testing the device with a multimeter in diode mode or picking an equivalent. Short datasheets may omit curves, so cross-check critical parameters with another source if the application is demanding.
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.