Should we have a fully automated or a semi-automated device? The difference between a fully automated and semi automated defibrillator is very small. The decision as to which one to choose is often down to personal choice and circumstances. Both have their advantages and disadvantages and it is important that you choose the type of defibrillator that best suits your needs and circumstances. The key difference between the two is that the semi automated device requires the user to manually press a button to deliver the shock. The fully automated device on the other hand, will tell you to stand clear and automatically administer the shock itself, if analysis has determined that a shock is required.