COM signal - When controlling the voltage generated, the ECM sends the target voltage data to the alternator via a PWM signal.

FR signal - The transistor activation signal inside thealternator monitors the voltage generated by thealternator to control the field current before itsends the FR signal to the ECM. (At certain RPM/electric loads, the FR duty can remain static. However, more often, the RPM, electric load, target voltage, etc. are always changing in the vehicle, so the FR must also change constantly)

L signal - Turns on the battery warning lamp on the dashboard when the battery charging system malfunctions. (Conditions for turning on the lamp - overcharge, over discharge, a field coil blown inside the alternator)

B+ terminal - The output voltage from the generator travels to the battery via the B+ terminal.