Datasheet for the EMB04N03H, a MOSFET from Excelliance MOS, provided as a 224 KB PDF. The part number suggests an N-channel device rated around 30 V, as used in notebook power circuits, and the sheet itself lists the exact ratings, package outline and pinout. Repair technicians consult it to locate the gate, drain and source on the board, verify switching behaviour with a multimeter or scope and pick a matching substitute when replacing a shorted transistor in a voltage regulator.
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 @ic_mosfet_pdf_datasheets. Enginerys does not host this file.
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The standard format for schematics, block diagrams, power-sequence charts and service manuals.