PDF identified only by the part number 2SD1877, listed as a schematic but in practice a datasheet for this 2SD-series NPN bipolar transistor. Devices in this range often appear in CRT horizontal deflection and power stages, though the name itself gives no ratings. Consult the sheet for collector-emitter breakdown voltage, current, built-in damper diode if present, and pinout, then compare these values against any proposed substitute before soldering it into an output stage.
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.