The Zoll AED Plus Semi-Automatic device has withstood the test of time and continues to be dependent up until this day. Audio and visual prompts help walk the user through proper treatment steps. Tells the rescuer at what point they should begin CPR to be most effective. Will tell the user when to administer shock, with a push of a button the device will delivery its energy to the patient. Low cost of ownership makes this a desirable device to own.