Four-Door Interlocking System – SM4C

  • Model: SM4C
  • Lock – Door: 4
  • LED indicators: 4
  • Cables: 4 meters
  • Material: Inox

Interlock System: A supplementary device designed to ensure that the doors of a room cannot be opened simultaneously, thereby ensuring isolation between clean and non-clean areas.


  • Installed in the control room of clean rooms, buffer rooms, airlocks, intermediate rooms, and changing rooms using a signaling system in the fields of healthcare, laboratories, pharmaceutical manufacturing, electronics, semiconductors, and office spaces.
  • Used for entrance doors, emergency exits, and safety doors.


  • Control device

  • Mechanical or electronic lock


  • When one door is opened, the other two doors will automatically close, and three doors cannot be opened simultaneously.
  • If one door remains open for an extended period without closing, an alarm will sound to remind staff to close the door, or the remaining two doors will automatically close.
  • In case of a power failure and for electronic interlock systems, all three doors can be opened to ensure user safety.
  • In emergency situations, an emergency button can be pressed to force open the door.


  • The interlock control unit will be installed on the ceiling panel, connected to an available socket (the shorter the distance between the control unit and the socket, the better, to save wiring costs).
  • Signal indicator lights will be mounted on the panel wall in an easily visible area when entering/exiting, typically installed next to the door panel.
  • The lock latch will be installed discreetly inside the panel (requires drilling and wiring), can be installed on the side or top of the door frame.
  • The latch positioning plate will be attached to the door leaf, corresponding to the latch installation area.

Sangma interlock systems from VCR are currently installed at pharmaceutical factories like Merap, Hanvet, Anvy, and Nam Ha.

Additionally, some installation errors to be aware of include:

  1. Securely fasten the signal connection wires to the latch and signal indicator — Error: The alarm will sound loudly and continuously.
  2. Install the latch and latch positioning plate in the same direction (Wifi symbol) on both accessories — Error: The latch will not function.
  3. Reverse the signal wires between the indicator and latch — Error: Installation is not possible. Note that the signal wire of the latch is usually slightly thicker than the wire of the indicator, please keep this in mind during installation.
  4. Use wire conduits and tubing to protect signal wires on the ceiling, preventing insect damage. Signal wires are different from power wires and can be difficult to reconnect if damaged.

Real-life images:

Interlock installed at the Merap pharmaceutical factory.

Interlock installed at the Anvy pharmaceutical factory.

Actual videos:

Choosing the right interlock system for cleanrooms.


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