Double-locking : Double-locking prevents the lock from being unlocked from the outside. You can enable it by using the [OPEN/CLOSE] button. Emergency Power Contact : Continuing to use the lock without replacing batteries when required will lead to the batteries discharging and cause the lock to malfunction. You can open the door by touching the external power contacts on the Exterior Unit with a V battery and then touching with the Card or entering the PIN Code. Indicator Lamp : Indicates the operational status when the Card is being read or the lock is in operation.