AEDs save lives, that goes without saying. But how do you know if your AED is working?

A recent trial of mobile defibrillator units (AEDs) during running events in Tokyo, showed a 100% survival rate from Sudden Cardiac Arrest suffered by athletes participating in the events.

A referee suffered a cardiac arrest during a charity football match, organised to raise funds for a defibrillator:

https://www.metro.news/referee-suffers-heart-attack-during-charity-match-to-raise-funds-for-defibrillator/1159446/