Port current supported by the board. The value ranges from 1 to 10,
which indicates the port current value supported under certain loopline impedance.
1 -- 25mA steady current
2 -- 16mA steady current
3 -- 35mA 2*200
4 -- 35mA 2*250
5 -- 35mA 2*400
6 -- 47mA 2*200
7 -- 47mA 2*250
8 -- 47mA 2*400
9 -- 17mA steady current
10 -- 20mA steady current