From reading the underlying article, it is apparent that the power source is externally available (since they monitored power consumption). Looking at the inst

From reading the underlying article, it is apparent that the power source is externally available (since they monitored power consumption). Looking at the instruction manual [1] confirms this; you do not need to open the lock to change the battery. So there is no mechanical lock fallback. The fact that you can remove the batteries (and even the number pad) without unlocking the safe does seem to present some DoS attacks, but I assume that isn't a major concern. [1] http://www.sargentandgreenleaf.com/pdf/630-302_6120_op.pdf http://www.sargentandgreenleaf.com/pdf/630-302_6120_op.pdf