The regulator monitors the excitation current as a function of the alternator output voltage.Very simple in design,the alternator with shunt excitation has no sustaining short-circuit capacity.Voltage Regulation:around +/- 0.5; Voltage supply/sensing range 85 -139 V (50-60Hz)Rapid response time (500 ) for a transient voltage variation amplitude of 20Voltage setting P1; Stability setting P2.Initial potentiometer settings :1) P1 potentiometer (AVR voltage adjustment): fully anti-clockwise.2) Remote voltage adjustment potentiometer: centre position. Run the alternator at rated speed. If the voltage does not increase, the magnetic circuit should be remagnetized (see section 2.3)3) Turn the AVR voltage adjustment potentiometer P1 slowly until the output voltage rated value is obtained.4) Adjust the stability setting using P2.5) Sealed potentiometer P3 is factory set at 48 Hz for 50 Hz and 58 Hz for 60 HzMaterial: plasticcolour: blackPackage Contents:1 x Automatic Voltage RegulatorOnly the above package content, other products are not included.Note: Light and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.