Primarily for doors which must always be latched (e.g. fire doors) and where deadlocking is needed. Function is determined by a sliding snib on forend. When the snib is in its up position, the lock will deadlock when the door closes and can only be opened by a key or by the thumbturn. When the snib is in its middle position, the lock will latch when the door closes but can be opened by the handles. The down position of the snib is not in use. Sliding snib is released only when turning the key (or thumbturn). Microswitch version. The switch changes it’s status when the latchbolt is fully extended. The lock case works with the 4613 and 4614 striker plates. Fire resistance: EI1 15-EI1 60 and EI2 15-EI2 60.