If the prefix to the forwarding command is "**" (instead of the usual "*"), then the phone number in that command is registered in the network. If after that the forwarding is deactivated using a command with a single "#", then later it will be possible to re-activate this forwarding again with a simple "*" command without a phone number in it. The forwarding will be re-activated to the number registered in the network. For example, if one uses the out-of-reach code in a forwarding command: