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 setting function, the I2C communication external storage read parameters, speed alarm Dynamic hysteresis