  Recently proposed information-exploiting systems designed to extract work
from a single heat bath utilize temporal correlations on an input tape. We
study how enforcing time-continuous dynamics, which is necessary to ensure the
device is physically realizable, constrains possible designs and drastically
diminishes efficiency. We show that these problems can be circumvented by means
of applying an external, time-varying protocol. This turns the device from a
"passive", free-running machine into an "actively" driven one.
