Front Sensor Kit - 4 Sensor 91CMD05-4F As this kit is designed for front fitment power is not taken from the reverse lamp power feed and rather taken from ignition with both brake pedal activation as well as offering a manual activation/deactivation button for added safety. After applying the brake pedal the system will activate and remain active for 15 seconds. If an obstruction is detected during this period the timer restarts for another 15 second cycle. If an obstruction is not detected the system reverts to stand-by mode. All 4 sensors must be fitted to vehicle. 1,2,3 or 4 sensors can be fitted to suit vehicle application and demand.