The black square device is the switching transistor thst controls field excitation voltage by turning on-off or in a current sinking circuit, the transistor actually supplies a VARIABLE DC Voltage to the alternator field via the green wire. The blue wires supply the system reference voltage. The small little components are called SMD or Surface Mounted Devices, which are resistors and capacitors that form the voltage divider network to control the transistor's conduction point and subsequently the alternator's field voltage seamlessly. Simple and usually reliable....but insure the regulator is securely grounded, either to the firewall or thru a separate wire to the block. Only a maximum of 5-6 amps are being controlled, a # 14 AWG wire will be adequate for the ground. Just my opinion of course.....
