1. The board is equipped with built-in charging management and charging and discharging protection 2. The calibration value is a six and a half digit count, accurate and reliable. According to usage requirements, it is recommended to recalibrate the calibration conditions every two years. The time and calibration value record card will be pasted on the benchmark 3. With indicator lights, press and hold for 2 seconds before turning on. When turning on, all four indicator lights light up simultaneously 4. This product is a precision voltage reference that can be programmed with four common output voltages: 10.0 V, 7.50 V, 5.00 V, and 2.50 V 5. Voltage output interface with 2mm copper test socket for easy insertion into a pen type multimeter for measuring or calibrating other instruments. Charging and discharging interface:micro-USB. Output interface:2mm banana socket Battery:300mAH benchmark dedicated battery (product does not include batteries) Battery voltage:3.7V Battery model:14250 Voltage:DC 5V Instructions: 1. The benchmark is not used to fully charge the battery every two months. The board is equipped with built-in charging management and charging and discharging protection. Please note that the battery polarity should not be reversed 2. The output interface is a 2mm banana socket, and there is also an SMA output interface calibration. The HP3458A eight and a half digit multimeter is used for calibration (after sufficient preheating), and the calibration value is six and a half digits for counting, which is accurate and reliable. According to usage requirements, it is recommended to recalibrate the calibration conditions every two years. The time and calibration value record card will be pasted on the benchmark, please keep it properly 3. Press and hold for 2 seconds before turning on the machine.