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.

  • I think there's a more generic question here about electronic beeps - are there any standards ? ( Eg does 1 beep mean success and say 3 mean failure ?)
    – PhillipW
    Apr 28, 2021 at 18:23

1 Answer 1


I'm working

The setup you describe requires two types of user feedback:

  1. "I've read your key"
  2. "Key OK"

The former also signifies "I'm connected to the electricity and operational."

First and foremost - consider accessibility. The visually impaired - or people whose attention is buried in TikTok on their mobile phone - would need some feedback to denote "I'm working and I've read your key". That's what the beep is for.

As for feedback for "Key OK" - could be a green light, or just the sound of the lock opening (if loud enough).

All is obviously depends on the other feedback the fob/door offer.

The Payment Terminal

I feel that the beep signal should always, and only, signify reception of the correct key.

Imagine you tapping on payment terminal and there's no feedback...

A contactless payment terminal

  • I in part agree. If the "I'm working" signal clearly signified I'm working then that is ok, (although still could be improved), however this is not the case with most fobs I've encountered. Many fobs indicate working or processing of the correct key and then do not unlock the door. This is the crux of issue and has resulted in very poor communication to users. (As a side issue, ultimately, the I'm working signal should not be necessary because the technology should be good enough to process keys so fast as not to require such signals.)
    – Ootagu
    Apr 29, 2021 at 3:59

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