1】DC-005 is a common type DC socket, with a supporting device of 5.5 plug, capable of automatically disconnecting the internal power supply of the circuit.Pin definition: (1) power positive pole;(2) negative static contact;(3) negative moving contact.See the figure below 

2】 when the plug is inserted, the top ③ start contact, cut off the circuit internal battery negative path, internal power supply stop power supply, then access to the external power negative pole, and ①、③ foot form external power supply path.Electrical wiring principle is shown in the figure below