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BT earpieces

Discussion in 'Electronic Design' started by D Yuniskis, Mar 24, 2010.

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  1. D Yuniskis

    D Yuniskis Guest


    Anyone dissected one of these? I'm curious if it is even possible
    to do so (or if they are so highly integrated that doing so just
    results in a pile of plastic and silicon). E.g., could you use the
    guts of the radio and interface the rest to an external mic and

  2. It probably depends a lot on the specific model. I have done it to a
    cheap Chinese one from DealExtreme:

    It wasn't even difficult.

    If look at the link, there are even a couple of decent quality
    pictures from its internals.
  3. You might have to be a bit more specific there Don.

    BT Earpeices could be a number of things.

    To some of us in UK they could be the British Telecom standard item for
    call-centre and switchboard personnel where they are on the phone for long
    periods of time. These are usually the Aerolite headset but there are a
    number of different makes and models available.

    Alternatively I suppose you could be looking at the Bluetooth devices make
    it seem that people are talking to themselves when they are actually talking
    on the mobile phones.

    I would expect that most of the latter ones use a cheap microscopic
    microphone element. If what you wish to do is connect a different microphone
    then I expect that should be possible. Sounds like you need some serious

    Paul E. Bennett...............<email://>
    Forth based HIDECS Consultancy
    Mob: +44 (0)7811-639972
    Tel: +44 (0)1235-510979
    Going Forth Safely ..... EBA.
  4. D Yuniskis

    D Yuniskis Guest

    Hi Robert,

    Ah, sorry, some confusion, there. My bad. This is more
    like what I was talking about:

    with the differences being:

    - smaller size (?)
    - microphone (i.e., duplex operation)
    - not a "music player", etc.

    I.e., the sort of thing you use with a BT enabled cell phone
    for "hands free" operation.
  5. D Yuniskis

    D Yuniskis Guest

    Hi Paul,
    Ah. No, BT == BlueTooth. My bad.
    Yes (good description! ;-)
    I've pulled apart some small voice recorder/MP3 player devices and
    the microphone in those was tiny -- though I could easily hold
    it in my fingers, unsolder it, etc. Most of the BT earpieces
    I've seen seemed a fair bit smaller, though. I was wondering
    if there was an even greater level of component intregration
    that would make attempts to *modify* them essentially fruitless.
    Ditto for the "earphone".
    Yeah, I was hoping to avoid dismantling one until I knew if
    that would be *likely* to yield promising results. :-/
    I guess it's time to make a sacrifice to the electron god...
  6. D Yuniskis

    D Yuniskis Guest

    Hi Brendan,

    Well, a package of that size wouldn't be too bad -- just like
    soldering SMT components.

    What I am more fearful of is this package being *integrated* into
    an SoC-ish implementation -- making the connections inaccessible.
  7. Probably smaller. But unless size is important, the bigger ones are
    probably easier to hack.
    Take a look at the pictures of the internals. You'll see the
    microphone soldered directly to the board, pointing sideways.
    This does both. You attach it to your shirt near your face. The mic is
    built into the unit. You can choose to connect mono or stereo
    earpiece, depending on wheter you want to talk on the phone or listen
    to music. The included earpieces sound horrible, though.
  8. D Yuniskis

    D Yuniskis Guest

    Hi Robert,

    I need to put this inside an existing (small!) container
    so the size of the item I cited was appealing.
    Ah, OK. I missed that in my first glance! Points *down*
    (in the photo I studied)
    Do you have to press any buttons to get it to *do* something?
    (i.e., can you just use it as long as power is available?)
    But, the *earpiece* was the problem, not the device?
    (i.e., if you had replaced the "earphone" -- which I
    intend -- then things would be better?

    Hmmm... maybe just buy one and take it apart...

  9. Nemo

    Nemo Guest

    I recall an old story about BT (British Telecom) microphones, back in
    the days when they were known as the Post Office... I heard this 20
    years ago when I worked in telecoms, and it was old even then.

    For several decades these were carbon, and had very uniform
    characteristics. Then one day someone noticed the frequency response was
    out of spec for all new ones. Engineers investigated and eventually
    zeroed in on the carbon itself, whose characteristics had subtly
    altered. Inspectors ended up in Wales where a coking plant created the
    carbon by anaerobic heating of coal or whatever (packing it into a
    sealed chimney and cooking it like a closed oven for a couple of days).
    And yes, the carbon was definitely different somehow. But following the
    manufacturing process from start to finish, they were at a loss to
    explain where the operators were deviating from the written procedures.

    Looking for correlations with events that happened around the time of
    the change, they discovered that it coincided with the retirement of a
    foreman. Further enquiries revealed he had a curious habit of "marking
    his territory" before each "shot", ie urinating on the pile of coal
    before it was sealed up. Experiment showed that this was, indeed, the X
    Factor which brought the carbon back into spec.

    And so BT continued making carbon mikes for many more years.
  10. If the phone is already paired and in range when the device powers up,
    it connects automatically. If the phone goes out of range and comes
    back into range, you have to press and hold the button to reconnect.
    To answer an incoming call, or to initiate an outgoing voice dial, you
    have to press the button.

    For music, I can't quite remember. I have tested it, but don't use it.
    Yes. I tried listening to music with a different pair of (also cheap)
    earphones (it's a standard 3.5mm jack), and they sounded fine.
    Considering the cost, the risk is minimal. You could even get a couple
    of different models to see which one is most suitable.
  11. D Yuniskis

    D Yuniskis Guest

    Hi Robert,

    The size and button issues look like deal-breakers. :<

    Thanks, anyway!
  12. Hmm. I'll test and see if I can answer the call from the phone. I
    expect that should work, but I have never (consciously) tried.
  13. Ok, I have tested. I can answer the call from the phone, but I cannot
    re-establish the connection after having been out of range.
  14. D Yuniskis

    D Yuniskis Guest

    Hi Robert,

    <frown> While I'll admit that I expected you would need to
    explicitly pair the device *initially*, I guess I am
    surprised that you have to repeat this procedure, again,
    when you "simply" move out of range.

    Or, am I misreading your statement: the device may
    remain paired but this *session* is "broken"? I.e.,
    you can "answer" the next call but can't "reconnect"
    to the current?

    (sorry, I don't mean to be splitting hairs -- but I
    *think* there is a difference?)
  15. You don't have to repeat the pairing (with PIN codes etc.). But it
    seems the phone is not aware that the headset is in range until the
    headset sends some sort of notification.
    I've never tried to go out of range during an ongoing call.

    There is a small icon (a headphone surrounding the BT logo) on the
    phone that shows that a BT headset is connected. If that icon is shown
    when an incoming call arrives, the BT speaker beeps to indicate the
    incoming call, and the call can be answered from the headset with a
    short press of the button.

    If the phone goes out of range, the headset icon disappears and does
    not automatically come back when the phone comes back into range. In
    this state, an incoming call cannot be heard or picked up from the
    headset. What you can do, is to press and hold the button for a couple
    of seconds to initiate the reconnect. That takes a few more seconds,
    and then you can answer the call.

    I know some BT hands-free units (which is essentially the same thing)
    will reconnect automatically when the phone comes into range. I once
    was in a conversation with a person who was walking towards his car.
    As he got close enough, the audio was automatically transferred to the
    HF inside the car, and we could not hear each other until he opened
    the door and got into the car.
  16. D Yuniskis

    D Yuniskis Guest

    Hi Robert,

    But, once the connection was made, why wouldn't it persist/resume
    *after* interrupted? Or, is it a duplex channel and the phone
    decides that it should close the session once the channel is
    broken (does your phone then reactivate the speaker/microphone
    in the phone "automagically" once the connection is "interrupted"?
    OK. So, the headset creates another "session" with the phone
    at that time.
    Hmmm... so, maybe the issue is in the *headset* trying to
    prolong battery life? I.e., when *it* no longer senses
    the BT connection as "live", perhaps it powers down? And,
    repressing the button powers it up and sets it hunting
    for its paired mate?

    <frown> I will have to play a bit to identify where the
    disconnect is happening.

  17. I don't know, but I presume it is to avoid spontaneous transfer to the
    BT unit if it should happen to come in range. Say I am talking on the
    phone while walking towards my office (where my BT unit is located).
    Once I get a few yards outside the door, I'd lose all audio.
    Yes, the phone automatically transfers to the on-board microphone and
    speaker. I don't have to do anything on the phone to get it working
    It does not look like it. The BT unit makes a specific type of beep
    when it is powered on (also by holding the button for a couple of
    seconds), but a different beep when only reconnecting a lost
  18. D Yuniskis

    D Yuniskis Guest

    Hi Robert,

    But, presumably, you can deliberately tell the connection
    to be made/broken. What I am saying is why wouldn't the
    device seek to maintain whatever mode of operation was
    in effect "prior to the (temporary) loss of signal"?

    I.e., you can pair the devices. Then, decide if (any particular)
    connection (call) should be routed over the headset or the
    phone itself. Once this decision is made, it should persist
    until you explicitly tell it otherwise. Yours seems to
    behave as if "loss of carrier" is the same as "I want you
    to disconnect". The former is something that the user
    has little direct control over ("don't wander *too* far...")
    whereas the latter is a very deliberate action (normally)
    on the user's part.
    But, the latter is still only done when the user
    "reinitiates" it, right?
  19. Yes, that decision is made by the phone (or it user). On my phone,
    that's relatively cumbersome, so switching the BT unit on and off is
    much easier, should the need occur.
    It' probably just a decision made by the firmware programmers. Other
    devices may be different.
    If I power off the phone to change SIM and then power up again, the BT
    connection is not lost. Maybe it has to do with the length of time the
    connection was interrupted or something.
    Yes, that's correct.
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