Indexed as a schematic, the 2SD1723 PDF of 146 KB is a component sheet for one discrete transistor. In the Japanese JIS system, the 2SD prefix identifies an NPN bipolar device for low-frequency service. It should list maximum ratings, electrical characteristics and a dimensioned outline showing each lead. Use it to verify orientation, test junctions with a multimeter and compare possible equivalents for voltage, current and gain. Look for D1723 printed on the part to confirm the identification first.
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.