※ IEC(International Electrotechnical Commission) defines protection structure of electric instruments or protection boxes as follows.

1st Digit	Protection against solid	2nd Digit	Protection against liquids	IK Code	Protection against mechanical impact
IP	TEST	IP	TEST	IK	TEST
0	No protection	0	No protection	0	No protection
1	Protection against solid objects up to 50mm, e.g. accidental touch by hands.	1	Protected against vertically falling drops of water.	01 ~ 05	Impact < 1 Joule
2	Protection against solid objects up to 12mm, e.g. fingers.	2	Protected against direct sprays of water up to 15 ° from the vertical.	06	Impact = 1 joule
3	Protection against solid objects over 2.5mm. (tools and wires)	3	Protected against direct sprays of water up to 60° from the vertical.	07	Impact = 2 joule
4	Protection against solid objects over 1mm. (tools, wires and small wire)	4	Protected against water sprays from all directions ㅡlimited ingress permitted.	08	Impact = 5 joule
5	Protection against dust limited ingress.	5	Protected against low pressure jets of water from all directions ㅡ limited ingress permitted.	09	Impact = 10 joule
6	Totally protected against dust.	6	Protected against strong pressure jets of water from all directions ㅡlimited ingress permitted.	10	Impact = 20 joule
		7	Protected against the effects of temporary immersion between 15cm and 1m in water.
		8	Protected against the effects of continuous immersion in water.