Model: LM2596 / Digital Tube Voltmeter Input Voltage: DC 4V - 40V Output Voltage: DC 1.5V - 35V (Adjustable) Output Current: 3A (max.) Conversion Efficiency: 92% (max.) Switching Frequency : 150KHz Press the Button in a Short Time (1 Second) so that IN Led Lighted, the Voltmeter shows the Value of Input Voltage. Press the Button in a Short Time (1 Second) Again so that OUT Led Lighted, the Voltmeter shows the Value of Output Voltage Rotate the top screw of Potentiometer Clockwise to Boost the Value of the Output Voltage, Anti-Clockwise to Reduce it Long Press the Button Between 1 and 4 Seconds to Turn Off the Voltmeter