Weekend, my friends and I have to work all day is the weekend, the feeling of shortness of breath to breath the fresh air, let all day in front of the computer eyes have a little rest, we decided to go for a walk in the park, get up early in the morning began to chat, according to the appointment time of departure from home, arrived at about good place, we entered the park, we walk, walk a friend suddenly fell down, it was found that a small black square thing to the trip, I do not know what it is, a friend told me that it was a power adapter , I went home to search on the Internet the power adapter , know the principle and usage of the power adapter , did not expect today also learned a little knowledge, really very happy, every day is a good harvest.