Incoming Telephone lines: Do you need Primary or SecondaryProtection?
线提供初级保护或次级防护？
2
PPE is a secondaryprotection for employees when engineering or administrative controls are not sufficient to protect employees.
在工程或管理控制不能充分保护员工时，个人防护用品作为员工的第二保护用品。
3
Each 500 kV transmission line will be protected by two primary pilot relaying systems with a backup relaying to achieve primary and secondaryprotection.