Designing User Interface for car keys

Here at Microsoft we have people called Program Managers (PMs) whose job is to design a product. They’re the ones that make a feature usable to the customer.


A remote keyless entry car fob is quite useful. It’s essentially a wireless short range transmitter that communicates a (hopefully) secure signal to a receiver in a car to signal locking/unlocking, open the door, trigger the alarm, etc.


I remember when I was a little kid that my dad used to get catalogs from a company called JC Whitney.  So I ordered a keyless remote control system and installed it in my 1990 wagon about 12 years ago. This was right after it was burgled at the University of Hawaii while helping my soon-to-be wife to move<sigh>. The doors were locked and the burglars jimmied and broke the lock, and stole a bag of my wife’s finest clothing and my $1300 cell phone (can you believe they’re essentially free now? The price of having your own consulting business.). Perhaps the burglars would have been scared away by the alarm.


The keyless remote entry was great: It had 2 buttons on the remote, only one of which was enabled. That button would act as a toggle. One hit, and it would toggle the locks. If it was locked, the car would unlock. And vice-versa.  Very simple.


(If you insert the key into the door of my 1990 wagon, twisting it twice would unlock the entire car, once would unlock just the driver door. Why would you want a partially unlocked car? Some PM must have received a bonus for that.)


Also, since I installed it, I had full control over its behavior. I found it very annoying that any time a car was locked, the horn would blare (or as the advertisers spin it, “chirp”), waking up the neighborhood. This was easy to disable: the circuit board had DIP switches on it, and one disabled this feature. (Remember DIP switches for PC boards?). Flashing the lights once for lock, twice for unlock is a great visual indicator of the lock state.


After it had been working for a few years, it failed for some reason. I was able to take it apart, reverse engineer the circuit board, determine that there was a cold solder joint, reheat it with a soldering iron, and it worked just fine.


Currently, my wife and I have 2 different cars from 2 different manufacturers. Each has a remote keyless entry fob, but the user interface design seems imprudent. Why is there one button to lock the doors, and a different button to unlock them?


That’s like having 2 push button light switches: one to turn on the light, and another to turn them off. In order to use the feature, you must look at the fob to figure which button to push. Not only that, the buttons are not in the same positions for each car’s fob.


Some remote controls have poor user interfaces. A TV control that has every button the same size comes to mind. This means you must look at the control to use it. A better design would be one that allows you to view the TV while surfing, or watch for traffic while unlocking the car. Button size, shape, texture and positioning seem like relatively inexpensive button characteristics to change. Using rocker buttons for Channel or Volume Up/Down seems to make sense.


One of our fobs is built right into the top of the key, making it a single piece unit. Nice. That fob also has a single button that opens/closes the power lift-gate so we can dump in payloads quickly. Oh why oh why couldn’t they have used one button to lock/unlock that car? Each car has a built in programmable pushbutton to close/open the garage door. It’s not two buttons: one to open the garage, the other to close it<sigh>. The word Panic is in red right on the button to lock that car, so my daughter asks me why you need to Panic to lock the car. It does say the word “LOCK” next to the button, but it has no color and is harder to read. Why does that button have two purposes: lock and panic?


In electronics, there is a nomenclature for switches. DPST means Double Pole Single Throw. SPST means Single Pole Single Throw. For this lock/unlock scenario, a momentary contact SPST would work fine for locking/unlocking. This is just like a doorbell.


When approaching the car, many remote fobs allow you to unlock the driver door only. You need to push twice to unlock all the doors. What’s the point of having a partially locked car? I can see that in some cases this is a desirable feature (when alone and its night and scary, but in that case I don’t think a partially locked car will help.) but in my case, I’d like the entire car to be unlocked with a single push. Perhaps this is the reason the designers wanted 2 buttons: a car can be locked, unlocked, or partially locked?


Also, when stopping the car engine, the driver door automatically unlocks. I’d like all doors to be unlocked when I stop. On one of our cars, various behaviors can be modified by programming the computer with a combination of pushing the driver door lock down, then up for a certain number of seconds to change to various modes. There is no F1 key for help for this feature, so it’s quite inaccessible.


A very convenient feature: One of our cars allows you to push the lock button to send a lock request to the car. If a door is still open, the request is queued until the doors are closed. This is a Very Nice Feature that is simple to design into the car’s programmable logic. Open the door, put the keys in your pocket, carry the groceries and kids from the back seat, kick the doors closed and it automatically locks. Without such a feature, you must have a hand free after closing the doors, which means your carrying capacity is reduced or you drop your kid.


Even rental cars come with remote keyless entry systems.


When’s the last time you actually used a key to open a car door?




Comments (14)
  1. Sherrod Segraves says:

    Two-button scenario: I don’t remember if my car is currently locked or unlocked, but I want it locked. My remote has two buttons, and I press the lock button. The car makes a noise (and/or flashes lights). The feedback tells me that it did what I wanted.

    One button scenario: I don’t know if my car is currently locked or unlocked but I want to lock it. My remote has one button, and I press it. The car makes a noise (and/or flashes lights). The feedback tells me that it did something. I walk away thinking I locked the car, but I forgot that (1) the car was already locked before I pressed the button, and (2) double-chirp meant that I actually unlocked it.

    The second scenario occasionally happens to my wife and me.

    The problem with a one-button remote is that uses have to (1) be aware of the current state of the car, and (2) pay attention to and remember the meaning of a sequence of noises and/or flashes.

    In my opinion, two-button car remotes are clearly better.

  2. Marcel says:

    I Used to drive a Renault Laguna (do you have these in the USA?). It’s the ultimate in remote key controls. You get a chip card which you (only the top models) carry with you. The door handels have sensors so when you move your hand it detects you have a chipcard and the door opens. When you walk away, the doors close. You can still press buttons for manual operations.

    I now have a ‘traditional’ key remote control. I spend weeks forgetting to lock the car!.

    When you are in the car, you insert the chipcard in the console and push the start button. Nice tough: you have to press start to stop the cars also, just like windows!

  3. Brendan says:

    Curse you Sherrod, you said what I wanted to, so… I’ll say it in a different way.

    With a light switch or a garage door opener, you are aware of the state of what you are controlling from a distance, on many newer vehicles who’s internal lock switches are farther down on the door, one would need to be quite close to the vehicle to determine it’s lock state.

    Under a single button lock system, one would need a way to verify the state remotely, the (un)popular method currently is the honking of the horn. Would you by default have the horn honk whenever the vehicle is locked remotely? For most users, multiple presses and possibly multiple honks would be required to ensure they are at the end state they want.

    To verify the state of my vehicle, I press the desired state button twice. In either case, it will flash the headlights and leave them on for 30 seconds beyond the last button press. If the lock button was pressed, a reassuring (and quite loud) horn blast occurs. While it may not be the most straight forward method, it is far better than the alternative of a single button.

  4. Eric Newton says:

    good reason for partially unlocked vehicle: auto door locks are EXPENSIVE. cost me $85 in just parts (no labor… did it myself), and could’ve cost 300$ or so… I’d much rather have a single one go bad then them all go bad

    and dont forget, the general populus dont wanna have to think about "are my headlights on?" they just want one button to unlock, one button to lock, another button to "pop the trunk" and so forth… K.I.S.S.

  5. Hank Fay says:

    I’ve read that the resaon for only opening the driver’s side door is so that once you are in the car, a car-jacker can’t slide in the other door, which you as the driver can’t reach from your seat.

  6. Randy Brown says:

    Speaking of bad design for auto keyless remotes, the other day I was out shopping and came back to find that my remote would not unlock the car. As has happened in the past, the battery was starting to die and didn’t have enough power to unlock the door. No problem, I’ll just use the key the old-fashioned way for manual entry. Bad idea! When you do this after auto has been locked via keyless remote, you trigger the car alarm. Apparently, opening the door with the actual key itself is deemed a security risk by the folks at Subaru :).

  7. Chuck Urwiler says:

    Randy, I’ve had to do this a few times with my car (it’s 8 years old now, time to trade in!), but I have a handy little button under the dash that you have to press at the same time as turning the key on in the ignition to stop the alarm. Were you able to do that iwth yours? Mine was put in after I bought it, sounds like the built-in alarms might not have this "feature."

    Nice to "see" you and Calvin here in cyberspace… feel free to drop me an email at chuck dot urwiler at MentisSolutions dot net!


  8. says:

    the panic can be very very loud because if some people

    heard the panic go off that means some people think that panic is so crazy. and it’s so loud forever?…..

  9. College Loan says:

    Very good details and new. keep it posted.

  10. thoughts from a professional developer

    I do not agree. Go to

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