voice control

Control of certain functions by the use of voice commands.

verification code

Code used to authorise the making of a calling card call.

validity period

Period of time during which a message that could not be delivered is saved at the SMS or MMS service centre in order for the message to be sent again.

username

Name that identifies a user to a computer network.

User ID

SEE DEFINITION FOR 'username'

unmute

To turn on the microphone again, after it has been muted.

unlock

To undo the lock on something.

unblock

To remove the restriction that prevents something from functioning.