What are the correct descriptions of the operations that should be performed before the communication device is powered up? (Multiple choice)
A . Measure the power supply circuit without short circuit between each other and the ground
B . Check the electrical connection is firm and reliable
C . The output switch of the power supply device is disconnected and the output voltage is normal.
D . Rated output current meets the requirements of powered devices
E . All power switches of the powered device are disconnected
F . Measuring no short circuit inside the powered device
Answer: ABCDEF