There are two types of modern AEDs:

• Escalating Energy AED:  This type of AED will automatically adjust and output (shock patient) with incremental strength of energies if needed.  These types of AEDs are more efficient.
  
  
• Non-Escalating Energy AED:  This type of AED is not capable of escalating energy shocks and it outputs only one strength of energy.  It lacks the ability to output incremental strength of energies if needed.

All of today's modern AEDs are:

• All modern AEDs will instruct you with easy to follow, step-by-step verbal instructions throughout the entire rescue process.
  
  
• All modern AEDs are programmed to deliver a shock "only" if the patient needs it. The decision whether the patient need the defibrillation shock is made by the AED and NOT by the rescuer.  Even if the rescuer accidentally presses the shock button, the AED will not deliver the shock.
  
  
• Have a non-rechargeable lithium battery.  Usually last 2 to 4 years in service and then it needs to be replaced.
  
  
• All electrode pads are single use only (disposable).  These have a sticky gel coating that can dry out with time, this is why these have an expiration date.
  
  
• All modern AEDs are Biphasic Waveform, which means, the electrical shock travels in the body from electrode pad A to pad B and then from pad B to pad A.