If your smartphone detects that an unknown AirTag, Ace Card or a tracker is traveling with you, it will send you a notification.After a while it will start playing a sound so you will be able to find it. These alerts are only triggered when the tracker is not connected to its owner's phone, so your partner's Ace Card will not trigger a sound if they are with you.These anti-stalking privacy protections are built in by Apple & Google in a cross platform collaboration.