many automatic defibrillators have periodic self-test function. If there is a malfunction or negative situation determined, then the user is warned by means of a red warning sign on the device. Hence, you should always put your AED defibrillator down a place where you can see and access it easily whenever required.
Please make sure that all disposable pads, accessories, and batteries are original. Otherwise, your AED may be out of order and this may cost a human life.