This is the place to find my reviews on BluetoothTM devices. I will have one soon about the Globalsat BTA-830, BTH-820, and BTA-809.
My interest in Bluetooth started with Bluetooth GPS devices. This along with Bluetooth cellphone headsets seem to be the most successful Bluetooth implementations. This site is a collection of reviews on Bluetooth devices. Another purpose of this site is to explain what Bluetooth is all about in layman's terms.
Bluetooth can be used to communicate between computers, computers and computer peripherals, cellphones, and lately audio/video devices.
Bluetooth has two purposes, one is to replace the cable that runs between two electronic units with a wireless connection and the other is to define a protocol to communicate on this connection. The replacement for a cable consists of a transceiver on each end that performs the signal connection at 2.4 GHz. This is a very low powered transmitter that is in an unlicensed band. There are two classes of service. Class one provides a connection of two devices up to 330 feet away. Class two requires that the two devices be within 32 feet of each other. The connection between a class one and a class two device is not defined but it is generally less that between two class one devices and more than between two class two.
While class two says the devices can be up to 32 feet (10 meters) apart the reality is often much less than that. In some cases they will need to be with 5 or 6 feet for good reception. The power consumption and power output for class two is really low. More on this later.
Profiles are used to define the kind of connection you have. In the world of cables this is often defined by using a different kind of cable, such as an audio cable or an ethernet cable. In Bluetooth this is done using profiles. There are many profiles defined for Bluetooth use and more are being added everytime a new version is released.
While profiles define the kind of communication between two devices some are intended for bi-directional data flow and some are intended strictly to send information in one direction. For example a stereo system might want to send audio output to a stereo headset. In this case the headphones could be thought of as a recipient of the data initiated by the stereo system. The stereo would be the output device while the headphones would be the input device. A device used to adapt a Stereo system to Bluetooth would be called a Gateway. Profiles include:
Each of these will be explained as I develop this page further. A particular device will likely only support a very small subset of the available profiles, perhaps only one.
V1.0 Bluetooth release only supported a few profiles, most notably the cellphone headset profile, and did not last very long in the industry. It was pretty hard to use. It had a maximum data rate of 768Kbps. It was ammended to V1.0B pretty quickly.
V1.1 improved the usablity, added lots of profiles, and provide a way to access the signal strength of the connection. The data rate didn't change. The usable data rate was often less than the maximum due to interference from other devices in the same 2.4 MHz band.
V1.2 did not change the data rate but added FHSP, frequency hopping spread spectrum. The 2.4 MHz band used by Bluetooth is pretty crowded with unlicensed transmitting devices and interference is likely. Frequency hopping provided the ability to switch frequencies in the band to avoid interference. Thus the full data rate was much more likely to be achieved. A few new profiles were added that took advantage of this better throughput. Stereo headsets (A2DP) were first supported in this version.
V2.0 + EDR (Extended Data Rate) jumped the transfer rate by 3 times to about 2.5 Meg providing for transfers that would not have been attempted at the lower rate. For example video was now possible. New profiles are constantly being proposed and added to the available capablities. Some implementations claim a 3 Meg rate.
This section will be expanded as time permits. It provides details on how each profile works.
The hands free profile Version 1.5 places some mandatory requirements on the hands free device and some mandatory requirements on the phone that supports hands free. The phone support requirements include many things that are optional in the hands free device so that if your hands free device supports it you will be able to use the feature on your phone. In addition some features depend on the ability of your service provider to support (Hold for example).
The mandatory hands free support includes the following servies:
More to come on this profile.
The AVRCP V1.0 profile provides support for a remote control using Bluetooth. It expects the devices involved to be either a controller or a target. It is possible for a device to switch roles for certain tasks. For the purpose of this profile target devices are divided into 4 categories, Recoder/Player, Monitor/Amplifier, Tuner, or Menu. One device may support more than one category. For example a tape recorder might also include a tuner. For each category there are certain minimum commands that must be supported and a list of optional commmand that could be supported. A device may also include custom vendor specific commands as well.
For each category the minimum commands are:
All of the categories may optionally support certain keys. The include the numbers from 0 to 9, dot, enter, clear, power, function keys F1 to F5, display information, help, and vendor unique keys. Unique keys must not do any of the standard functions.
The first three categories may also support sound select and input select.
The recorder/player category can add any of the following optional commands: pause, record, rewind, fast forward, eject, forward, backward, angle, subpicture.
The monitor/amplifier category can add any of the following optional commands: mute. Note that tone controls and equalizers are not defined but would fall into the category of vendor unique.
The tuner category can add any of the following optional commands: previous channel, angle, subpicture.
The menu category can be used by any device that needs on screen menu display. It can add any of the following optional commands: right-up, right-down, left-up, left-down, setup menu, contents menu, favorites menu, exit, page up, page down.