Fobs typically emit an audible sound, usually a beep, to indicate they have read the key which was swiped. The fob then unlocks if the key swiped was the correct key. Therefore, logically speaking, the beep signal of a fob should indicate that the key has been read by the fob. However, I have found consistently across many fobs that if you swipe the correct key "too fast" the fob will emit the receive key signal, but will not unlock the door.
My question is, what should the beep signal signify to the user? I feel that the beep signal should always, and only, signify reception of the correct key. I see no reason for fobs to beep either for an incorrect key or for an inconclusive swipe. In fact, the crux of my question could be phrased thus: "Should an inconclusive swipe, and a conclusive swipe of the correct key both be signified by the same beep?" I have observed countless times when users hear the beep of a correct key swipe then proceed to open the door only to find it locked and have to swipe again.