What Matters


Interlocking Door Systems Protect What Matters.

Interlocking door systems are being used more frequently for facilities requiring safety and security. Airports, courthouses, strategic installations, bio-medical facilities, and more commonly banks and credit unions are incorporating interlocking door systems to provide safety and security of their facilities. While some projects use standardized specifications developed by the owner from prior sites, others may require unique requirements that Isotec will translate into a site specific engineered system.

Simple two-door, one-room interlocks are familiar to some. System complexity increases dramatically as more related doors, screening sensors, connecting rooms are added. Isotec also designs for automatic door operators, card access systems, etc., with interlocking doors, to ensure compatibility, and satisfy local building codes.

The following is Isotec’s comprehensive regimen to engineer interlocking doors systems. Isotec’s expertise for engineering site specific door, hardware and component configurations is unsurpassed.


Define the Objective: Some interlocking door systems are for security in applications such as detention centers, casinos or government sites. These typically incorporate credentialed access and require that both the doors be normally locked. Bio-medical and pharmaceutical sites, on the other hand, may use a combination of locked and unlocked doors to provide a higher degree of security and isolation but using some normally unlocked portals to facilitate faster traffic flow.

Door Functionalities: The next step in designing an interlocking door system is to determine a facility’s occupancy and required door throughput. A site survey or Forward Observation of the site is best to determine the required design, functionalities and through put requirements. Floor plans, blue prints or “as built plans” detailing access points help to determine the required Programmable Logic Controller’s (PLC) ladder logic.

Door Status and Operation: For security purposes one door is normally locked. Opening either door causes the other door to lock, preventing it from being opened while the first door is open. Isotec programs door systems to be “fail safe”, meaning that both doors automatically unlock in the event of emergency or override.

Monitoring Door Status: Isotec uses PLCs to monitor and control interlocking doors. The PLC operates in accordance to pre-determined algorithms to meet the scenario of operation required by the end user.


Available hardware: Isotec primarily uses magnetic locks (AKA maglock) to secure swing doors. The maglocks have a minimum 1200lbs “pull force” rating. Higher levels of pull force are also available. Isotec may also use a combination of “door strikes”, fail-safe maglocks and fail-secure strikes. The combinations used are determined by the security requisites and life safety codes.

Credentialed Access: Credentialed access can be a biometric, PIN or card driven, used with an interlocking door system. Double “positive ID verification” is often used. The credential(s) are used as a request-for-access. Valid credentials will activate lock relays for a preset time. If the related doors are secure, the PLC will unlock the door following the state of the request-for-access input. Multiple requests-for-access are held pending until the door can be unlocked or the access request times out.

Automatic Doors: Automatic pedestrian doors require special considerations. Automatic swing doors are typically powered open and powered closed with a built-in time delay and various safety sensors.

Status Lights: Isotec uses Light Emitting Diodes (LED) status light displays to indicate if a door is locked (red light) or unlocked (green light). Depending on the required “scenarios of operation, some systems may use three colored status light displays (red, amber and green).


Emergency Overrides: In an emergency, the fire alarm relay on the lock power supply is used to unlock maglocks and failsafe strikes. Other override controls are programmed into the operator console and wireless push-button remotes included with each system. Time-delayed relocks to override the door interlocks, or a custom PLC sequence of operations are specified by the end user.

Security is a concept, what’s yours? It is critical to understand a facility’s safety and security protocols to properly engineer an interlocking door system. Designs and functionalities will vary as based on the needs of the facility and the end users concept of safety and security.

Call Isotec today at (303) 974-7699 for a free consult about your objectives.

Government Interlocking Doors

Isotec Security’s Safety Entrances® and Exit Lane Breach Control Systems (ELBC) are Designated Anti-terrorism Technologies by the Department of Homeland Security. Qualified Federal, State and Municipal agencies may purchase Isotec’s standard and site specific DHS Designated Safety Entrances and Exit Lane Breach Control systems directly at, keyword search, Isotec Security.

Commercial Interlocking Doors

DESIGNATED TECHNOLOGIES FOR YOUR SAFETY – Isotec’s Single and Two Lane, Designated Safety Entrances®, with Exit Lane Breach Control (ELBC) systems have been recognized by the Department of Homeland Security as Qualified Anti-Terrorism Technologies. Our two lane Safety Entrances® provide a weapons control lane and exit lane to accommodate higher foot traffic. Exit Lane Breach Control is built into every Safety Entrance® to stop persons from entering through the exit lane. Our systems interlocking doors can be built to withstand up to UL Level III specifications; .44 Magnum round with a muzzle velocity of 1,418 FPS.

Access Control System Products

Isotec’s automated Safety Entrances® provide a high level of security by interlocking two or more programmed doors and allowing only one door to be opened at a time. These standards or configured site specific systems are available as complete units or as a components package.

Call today (303) 974-7699

for information or email