A 124 KB PDF covering the 1SV128, filed in the schematic category but most likely a manufacturer data sheet for a single diode. The 1SV designation follows the Japanese JIS scheme and belongs to Toshiba's variable-capacitance diode range. The file name states nothing beyond the part number. Open it in any PDF reader to look up absolute maximum ratings, the capacitance curve and the package outline. These figures matter when judging whether a substitute will keep a tuned circuit on frequency, so check them before swapping parts.
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.