The safety rope is a protective device to prevent the operator from falling. Because the higher the height of the fall, the greater the impact, therefore, the safety rope must have the following two basic conditions:
1) it must be strong enough to withstand the impact of a fall;
2) to prevent the body from falling to a certain limit that can cause injury (i.e. it should be able to pick up the body before this limit, and not fall further). What this condition needs to explain again is, when human body falls from height downward, if exceed certain limit, even if pull a person with rope, but because the impact force that receives is too big, also can make human body viscera damage and die. Therefore, the length of the rope should not be too long, there should be a certain limit.