What does the FP2108T Ic do?
Futaba is a known brand of consumer radio control equipment.

The schematic using the IC you linked to seems to indicate that it is a complete Radio control encoder and modulator.  It will 'measure' the joy-stick positions with potentiometers and provide some other features and then generate a baseband or encoded servo control sequence. If I had to guess from the schematic style (age) I would say a generic 2 (perhaps even 3-6) channel analogue PWM system.