Lockedclosed

Lockedclosed is a term used to describe a state of a mechanism, device, or resource in which both locking and closing conditions are engaged, preventing access, use, or modification. The term emphasizes that neither reopening nor unauthorized access is possible until the appropriate unlocking action is performed, even if the mechanism could otherwise respond to other commands.

In physical contexts, lockedclosed commonly applies to safes, valves, doors, or containment systems. When a device is in the lockedclosed state, attempts to open or operate it are blocked by the security or safety interlock. The state is typically entered to ensure safety, prevent tampering, or preserve contents, and exits only through a defined unlocking sequence or override procedure that restores operability.

In software and digital systems, lockedclosed can describe a resource that is both closed and protected by a lock or permission constraint. This state is often represented in a resource lifecycle as a two-step barrier: a close operation followed by a lock. Access to the resource is denied until the system executes an unlock and then an open operation, or an explicit override. Implementations often employ a state machine to enforce valid transitions and to avoid illegal states such as opening while locked.

Designers use the lockedclosed concept to model safety-critical workflows and access control, ensuring that closing a resource automatically secures it against unauthorized interaction. Related concepts include the separate states of locked and closed, as well as lifecycle management and concurrency controls. See also: state machine, access control, lifecycle management.