非接触式欠速检测，非接触检测速度，4位薄码开关设置欠速比（8档位），4位LED串行动态显示，按键设定功能，I2C通讯外部存储读取参数，速度报警动态回差功能-Under speed detection of non-contact, non-contact detection speed, four thin code switch settings less speed ratio (8 stalls), four serial dynamic LED display, the key sett