to pair two devices using bluetooth, both have to have the same code entered. i think its done to make sure that if your in a croweded area, you dont try to pair up with a device close to you thats of the same kind or something like that.

as in, you have two devices. say a phone and a tablet. on each you enter the same code, and this tells each device that the other is the one its supposed to pair with.

some devices, like headsets, have a set code (often 0000) that they use. some keyboards have this, others do not. this because a keyboard has a way to enter a specific code. only problem is that they do not have a display to tell you if you enter the right code, or that its expecting you to enter a code at all...

the thing to remember there is that your not trying to enter something on the other device. your just telling each device what code to expect from the other one.

i guess one can compare it to a agreed handshake between people, so that they know they have found the right person or something like that.

it seems that this is the one thing that trips up most people when it comes to bluetooth, and probably the reason why the bluetooth SIG (the group that sets the bluetooth standard) is working on a wait to pair devices by bringing each device close together or into contact with each other.