Backlight control: Short press the key to turn on or turn off the backlight. Reset Energy: Long press the key for more than 3 seconds to reset the energy. Current Indication: Current has direction indication; if indicated, the current is in reverse direction, otherwise it is in forward direction. Energy Indication: Energy has direction indication; if indicated, the energy is in reverse direction, otherwise it is in forward direction. The energy direction is determined by the current direction. If the current is positive, the energy increases, up to a maximum of 999kWh, and will hold at overflow unless reset. If the current is reverse, the energy decreases, down to a minimum of -999kWh, and will hold at overflow unless reset. Working Mode: Direct power supply via test voltage. Data Preservation: Energy data and backlight state are retained when power is off. Model: 0-300V 100A / 300V 50A Color: Black Material: Plastic Package Contents: 1 x Host 1 x Line 1 x Wrench Only the items listed above are included; other products are not included. Note: Lighting and display differences may cause slight variations in color between the image and the actual item. Measurement error allowance is +/- 1-3 cm.