LEHMANN Smart Secure Smart Secure by LEHMANN enables you to control the security of your cabinets and storage units with your smartphone. Using the latest Bluetooth low energy technology, LEHMANN M300 and M400 Series Smart Secure locks can be locked and unlocked, either individually or in groups. LEHMANN Smart Secure offers many useful features, such as: - Simple security management, even for complex user configurations - Optional proximity locking and unlocking, with individual range control