Turn the (Under-Frequency Roll-Off / Low-Frequency Protection) pot slightly clockwise to match your operating frequency (50Hz or 60Hz).
Independent Red (+) and White (-) wires ending in spade terminals usually attach to the generator's slip rings (F+ and F-) to provide DC excitation to the rotor. an-5-203 avr wiring diagram pdf
and Line 4 (Blue) serve as the primary power input terminals for the AVR. Excitation Output (F+ & F-): an-5-203 avr wiring diagram pdf