An interlock door — also known as SAS, airlock, mantrap or interlock door — is an access system designed to ensure absolute control of passage between two spaces. Its operation is based on a fundamental premise: two or more doors can never be open at the same time. In this way, an intermediate enclosure is created that ensures physical separation between zones and prevents unwanted simultaneous access.
In practical terms, an interlock consists of two doors electronically controlled by a logic that allows one to open only when the other is completely closed and verified. This mechanism ensures that the system maintains tightness, security or environmental separation, depending on the application.
How does an interlock door work?
The operation is simple but highly effective:
- If door A is open, door B remains locked.
- Once door A is closed and its status is verified, door B can be opened.
- Sensors, electromechanical locks and control modules ensure that the sequence is followed without errors.
- Additionally, these interlocks can be integrated with access control systems, industrial PLCs, biometric readers or positive/negative pressure systems, depending on the requirements of the environment.
What is an interlock door for?
Interlock doors are used in situations where precise control of the flow of people or materials is needed, whether for reasons of:
- Security, to prevent intrusions or simultaneous access.
- Hygiene, in areas where sterility must be maintained.
- Environmental control, such as regulating pressure, temperature or particles.
- Asset protection, for example in access to vaults or critical areas.
Where are they used?
Applications are very varied and cover high-demand sectors:
- Banks and security vaults.
- Laboratories and clean rooms.
- Hospitals and surgical areas.
- Logistics and industrial centers.
- Corporate buildings and smart facilities.
- Prisons and high-security environments.
Why do they require specific types of locks?
To operate correctly, interlocks need locks capable of:
- Exporting the status of the latch and door to the control system.
- Receiving external commands (open, lock, timing).
- Synchronizing with the interlock logic, ensuring the correct opening sequence.
- Preventing simultaneous openings, preserving the integrity and functionality of the interlock.
In summary, interlock doors are a key piece in any facility where security, environmental control or access management are priorities. Their use, combined with advanced electromechanical locks, allows for the creation of highly reliable, efficient systems adapted to the needs of the most demanding environments.
BO Series – Our solution for interlock doors
The BO Series is an electropiston lock created to operate within advanced control architectures. Its features not only guarantee secure locking but also precise electronic communication, essential in systems where the opening sequence must be coordinated without margin for error.
Advanced interconnectivity
The BO Series incorporates two connection terminal blocks, a key feature that allows for independent management of:
- The lock's own control and status signals.
- External commands and feedback from the interlock system.
This design allows for seamless integration into complex access control systems, ensuring that the lock can communicate effectively with other components such as sensors, PLCs or biometric readers, which are often part of interlock door installations.
Real-time monitoring
Thanks to its two monitoring outputs, the lock can report accurately:
- The status of the bolt (extended or retracted).
- The status of the door (open or closed).
This level of information is essential in solutions where state verification must be immediate and reliable, allowing the system to make secure decisions.
Integrated timing
The BO Series includes a configurable timer at 0, 2, 5 or 8 seconds, allowing for precise control of the opening and closing sequence. This feature is particularly useful in interlock systems where timing can be critical to ensure that one door is fully closed before the other can be opened.
- Control how long the mechanism remains released.
- Adjust the behavior to the operational flow of the system.
- Prevent the opening from remaining active longer than necessary.
This is a function built directly into the lock, eliminating the need for external modules.
Intelligent multi-voltage design
With a wide operating voltage range (12-24V DC), the BO Series is designed to be compatible with various control systems and power supplies commonly used in interlock door installations. This flexibility allows for easy integration into existing infrastructures without the need for additional converters or adapters.
- An optimised design that ensures consistent performance across the entire voltage range.
- Slim housing of just 24 mm - suitable for narrow profiles.
- 100% reversible - flexible installation without restrictions.
- Stainless steel construction for strength and durability for intensive use.
- Fail-secure and fail-safe options to suit requirements.
The Series BO offers these versions:
- BO400 – Fail-secure: remains closed without power.
- BO500 – Fail-safe: unlocks without power for evacuation.
In summary
Thanks to all these features, the BO Series locks integrate optimally into interlock door installations, ensuring precise and secure operation.
Additionally, it is a maintenance-free solution with enough flexibility to adapt to existing systems, reinforcing its value as a reliable and durable option for advanced access control projects.