Covering the 2SA1242, this 212 KB PDF carries only the part number in its name, so it is best treated as the component datasheet despite the schematic label. A 2SA code under the Japanese JIS system denotes a PNP bipolar transistor. Repair use centres on the pinout diagram, collector-emitter voltage and current ratings, dissipation limits and package drawing. Bodies often carry just A1242, so read the marking carefully and match the gain grade suffix where the original part shows one.
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.