A demonstration slate train comes off the single line at Quarry Siding loop, headed by no.3. The up passenger waits patiently and is headed by no.6 "Douglas" The fireman of no.3 is exchanging tokens with the blockman. The token from the down train, having been first passed through the token instrument, is then handed to the up train giving it authority to eneter the single-line section. Meanwhile, the down train proceeds with the token that had brought up by the up train. Got it?