US Patent 7290418 Programmable lock with a controlled programming position

A key-operated lock that can be programmed for use with one of a plurality of user keys without disassembling the lock or replacing the tumblers. The lock operates with a user key so that the lock plug turns only in one direction to unlatch or unbolt, and can not operate or rotate in the opposite direction. The lock also cannot be programmed or reconfigured with an operable user key. The lock is typically manually latched or bolted into a locked configuration. The lock is configured to permit rotation in the opposite direction only when using a programming key, which can reconfigure or program the lock for use with another user key.