1.Backlight control: Short the key to turn on or turn off the backlight. 2.Reset Energy: Long the key over than 3 seconds can reset the energy. 3.Current Indication: Current has direction indication, if there is "-", it means the current is reverse direction, otherwise it is forward direction. 4.Energy Indication: Energy has direction indication, if there is "-", it means the energy is reverse direction, otherwise it is forward direction.The energy direction is judged according to the current direction, If the current is positive, the energy increase, maximum is 999kwh, overflow be maintained, unless you reset it; if the current is reverse, the energy decrease, maximum is -999kwh, overflow be maintained, unless you reset it 5.Working Mode: Direct power supply: Direct supply by test voltage 6.Data Preservation: Energy data and backlight state can be saved when power off. model:300v 50A Colour:black Material:plastic Package Contents: 1 * host 1 * line 1 * wrench Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.