There are times when it would be convenient not to be connected to the cellular network. Not just silent, but actually completely disconnected so the network can't see me. But with the N900 still functioning as a computer (which is what I bought it for in the first place). Is there a way to do this apart from taking the SIM card out? That would work, but as the SIM's behind the battery would require a power-down first, which I don't want. Thanks.