I tried to come up with a simple way of explaining what is happening, but all I could come up with takes a lot of explanation of how the Bluetooth hand [*]I don't know about your Plantronics headset but mine will automatically send the disconnect signal when they power down due to low battery shaking works. THIS IS NOT PAIRING - which is a separate process.
  1. ASSUMPTIONS
    • Assuming a paired device
    • Like all wireless devices Bluetooth is power hungry
    • Battery conservation is a very high priority and that is a major driver in how connections are made and maintained
  2. ESTABLISHING THE CONNECTION
    1. When the external device is initiall powered on it transmits a signal that essentially says here I am, I am Plantronics Headset with this Bluetooth address/identifier
    2. Every other Bluetooth device within range checks to see if that identifier is among the list of devices it is paired with
    3. If there is a match then a connection is established.
  3. MAINTAINING THE CONNECTION
    1. Once the connection is established there is no back and forth communication between your Plantronics headset and your iPhone, unless there is a call in progress, both devices assume the other is still there and ready to operate
    2. Both devices listen for a signal from the other paired device/
    3. Either device can initiate a call by sending a signal to the other device telling it to "wake up" and handle the traffic.
    4. If the devices get "out of range" of one another neither is aware of that and both continue to wait patienty for a signal from the other device
  4. NORMAL DISCONNECTION
    1. IF the Plantronics is powered down normally it automatically sends a disconnect signal to the iPhone and the iPhone disconnects the device.
    2. I dont know about our Plantronics headset, but mine also send a disconnect signal when they automatically power down due to low battery.
    3. This only works when the paired devices are within range of one another
  5. ABNORMAL DISCONNECTION
    1. An abnormal disconnection occurs any time your iPhone does not get a disconnect signal from your Plantronics headphone. This could be due to any number of reasons such as being powered down when out of range, failure to send a disconnect when it powers down due to low battery, or whatever.
    2. This leaves the iPhone believing the Plantronics is still connected and the default I/O device even though it may be powered off or not even present.
  6. SOLUTION
    • Be sure to shut down normally — I don't know about your Plantronics but on my devices that involves pressing and holding the power on button until you hear a descending musical tone.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein