The 2SD1622 PDF, 138 KB in size, sits among schematics, but a file named only by a semiconductor part number is very likely the device datasheet. JIS designation 2SD stands for an NPN bipolar transistor for low-frequency applications. Technicians consult it for lead identification, maximum collector voltage and current, dissipation and gain classes when diagnosing a shorted or open junction. Open it in a standard PDF viewer, and note the component may carry only D1622 on its case.
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.