Wireless Waterproof with LCD Backlight 25 Multi Function Bicycle Computer Speedometer auto wake up (Yellow) Automatic Wake-up, Maintenance reminder, Low battery alert 25-function bike computer for improving workout efficiency.Wiress Data Transmission, no wire needed, easy to install. Waterproof and Shockproof: Sophisticated techonology, interfaces seamlessly. Riding in a rainy day is also ok. Multifunctions: Odometer/CLOCK/Trip Distance/ Elapsed Time, Current / Average / Max Speed, Min/Max Tem ,etc. The switch of this bike computer is automatic awake, there is a small steel ball inside to realize it. So when receiving signals, the steel ball will shake.