Filed under schematics, though the file name is simply the JIS part number 2SD1903, so expect a component datasheet in this 131 KB PDF. JIS designations beginning with 2SD cover NPN bipolar transistors for low-frequency service. When replacing a shorted or open transistor, a technician consults the sheet for pin assignment, package drawing and electrical limits. Note that markings on small packages are often abbreviated, dropping the 2S, so read the body text carefully and confirm the rank or suffix matches.
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.