Component reference for the 2SC3124, a 294 KB PDF indexed as a schematic. The JIS 2SC designation identifies it as an NPN bipolar transistor, normally marked C3124. No package, grade or manufacturer appears in the name, so consult the document for those. Technicians rely on this sort of sheet to find the collector, base and emitter before meter testing, to compare ratings with the voltage present in the circuit, and to judge whether a cross-reference part is a safe substitute for a failed original.
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.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.