A TS device can have up to TS level documents, so unclass, secret, TS, etc. An unclass device can only contain unclass documents. So the device can have documents that go down. It should be physically impossible for someone on an TS device to email someone on the Internet. Therefore, if a TS document ever makes it on to an unclassified machine someone screwed up (maybe with a scanner or CD drive or something). That someone could have been either the sender or the receiver.