BA1404 reference PDF, 140 KB, for the ROHM FM stereo transmitter IC often used in small hobby and consumer FM transmitter circuits. Listed as a schematic, it probably contains the datasheet with pinout, block diagram and an application circuit. Technicians use it to check the supply and oscillator connections, follow the audio inputs and stereo multiplexer pins, and compare component values with the reference design when output is weak or the transmitter will not lock onto a frequency.
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.