This type of strainer is usually installed upstream of most of the devices in the system including the meters , backflow preventers ( or detector check valves ) and flow alarms , in order to protect these devices from damage caused by large particles 这种类型的过滤器通常安装在系统内大多数设施的上游，包括仪表，防回流阀（或检测止回阀）和水流警报装置等，从而保护这些设施不会被大颗粒损坏。
The model of safe following distance can not only avoid the accidents from back vehicles but also have no effect on the capability of traffic . with regard to some design of the model of safety following distance , i have made the scientific questionary in order to know clearly and accurately the habit operation of driver 建立车辆安全跟车模型时，作者做了科学的驾驶员问卷调查，从而使其能清楚、准确地反应出驾驶员的习惯操作，为高速公路预防追尾碰撞警报装置的开发研究提供了依据。
