HP iPAQ h5400 Series Reference Manual page 112

Require a Passkey or Bond to Access Services
To establish a connection, the other device must have a passkey or
an established bond for added security. You can add data
encryption to this type of security.
A passkey is a code you enter to authenticate connections
requested by other devices. The passkey must be known and used
by both parties or the connection will not be allowed.
If...
Both devices successfully
enter the known passkey
You want to require a
passkey exchange each time
you transmit information
To require a passkey or bond:
1. From the Today screen, tap the Bluetooth icon.
2. Tap the tab for the service you want to enable: File Transfer,
Information Exchange, Serial Port, Dial-up Networking,
Audio Gateway, or Personal Network Server.
3. Select Authentication (Passkey) required.
4. Select Encryption Required if you want to require all data
exchanged between the devices to be encrypted.
5. Tap OK.
Reference Guide
Then...
A bond is created between the devices.
You do not have to enter the passkey
again to exchange information.
You must remove the bond ("Unpair
Devices") prior to establishing the
connection.
Using Bluetooth
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