1, with test pencil first find out the wire;
2, turn off the power supply socket;
3, the wire connected to the switch is one of the two holes A tag, then pick out A from another hole was 2.5 insulated wire access L in the following three hole socket hole after prison;
4, to find the zero line of direct access to the three hole socket N hole after prison;
5, find out the ground directly connected to the outlet bore three E of inscribed.
Note: zero, ground wire cannot be wrong (generally face left zero right fire ground socket, or plug in electricity equipment, the open will trip.