Creating an Interlock Using U-PROX Equipment: Step-by-Step Guide

This document outlines three possible configurations for implementing an interlock system using U-PROX equipment. These are basic schemes that can be either adapted to specific user requirements or used as ready-made solutions.

The legacy interlock setup guide from the earlier “Golden Gate” system (Golden Gate 2002) is available in the standard document “Tambur.pdf” — it remains fully compatible with U-PROX IP400 controllers.

In addition, the document includes:

• a 3-door interlock wiring diagram,
• an implementation option for a large number of doors (from 2 up to an unlimited number)

Variant І.

Refer to the document “Tambur.pdf” available at the following link:
https://drive.google.com/file/d/14_ZqKaKDWtuYXnXKTQMwEbRYhTz4MX2-/view?usp=sharing
У ньому представлено найпростіший варіант реалізації тамбур-шлюзу з базовою логікою роботи.

All other aspects can be customized by the user based on specific needs and the required logic of the installed equipment.

In the provided example, cards assigned with the “security service” attribute are granted access even through locked doors.

Питання/Відповіді:

We faced the following problem:

1 – If someone leaves one of the doors open, will the second door be blocked from opening?

Yes — this is the basic interlock logic.

In the example provided, cards assigned with the “security service” attribute can override this restriction and open any door, even if the interlock condition is active.

To prevent undesired scenarios, we recommend:

• Installing door closers to ensure that no two doors can remain open at the same time.
• Connecting the blue wire of the reader to a normally open magnetic contact (MC) mounted on the door and wired to the controller’s ground (GND). When the door is open, the MC will short to ground — this can activate a continuous buzzer or any other attention mechanism.
• Keeping the “door held open” alarm enabled — if the door remains open for too long, the controller can trigger an alarm signal. In this case, you should:
  • Add the “alarm cancel” attribute to specific cards, or
  • Manually cancel the alarm via software.
• Setting up a filter for these doors in the alarm event window so that staff can see these events in real time.
• Enabling audible alerts in the software for relevant alarm events.

2 – What happens if employees attempt to open the doors from both sides simultaneously (entry/exit)? Will this break the interlock logic?

Yes, if both doors are opened at the same time, the interlock logic can be bypassed and both doors may open.

To avoid this, you can modify the circuit so that when one door is granted access (relay is activated), it simultaneously interrupts or shorts the blocking zone for the opposite door. This approach eliminates the risk of simultaneous opening.

3 – What if someone opens and closes the door without actually entering the interlock area? How to reset the interlock in such cases? Can additional readers be used?

No logic error occurs in this case:
– Once the door is closed, the controller automatically returns to “standby” mode and is ready to accept a new valid credential.

• Install a presence detector inside the interlock area to block both entries until the person exits.
• Use separate relays for entering and exiting the interlock zone.
• Connect the presence detector to a free input zone on the controller and configure it as “notification”, so the software can display real-time presence inside the interlock.

Logic for 2-door and 3-door interlocks is similar; differences lie in wiring details:

• Blocking opposite doors using magnetic contacts (MCs):
  Install MCs on each door to physically block access from two opposite directions. This is done by interrupting the GND line in two separate zones on different controllers. Keep in mind that blocking may come from either side. See wiring diagram below for clarity.
• Door status indicator on hardware level:
  If you want to monitor actual door state, add a separate MC configured as a sensor for each door. Its output is not connected to any other circuit.
• Other settings:
  – Exit via button or reader,
  – Additional access modes — optional and customizable based on user preferences.

The 3-Door Interlock Circuit Is Based on the Standard 2-Door Logic

For proper operation, 4 kΩ resistors are used, connected in parallel within the blocking zone, giving a combined resistance of 2 kΩ.

When one of the parallel resistors is disconnected (via a magnetic contact on a door), the total resistance in the zone rises to 4 kΩ, triggering the “blocking” mode in the interlock logic.

When one door (e.g., D1) is opened, the corresponding magnetic contact (MC) disconnects its 4 kΩ resistor.As a result, on the other doors (D2 and D3), the blocking zones (Z1 on C2 and C3) are left with a single 4 kΩ resistor each.From the controller’s perspective, this is interpreted as an open circuit — which activates the “blocking” zone condition. Consequently, access through those doors is denied until the first door is closed and the circuit is restored to its normal 2 kΩ resistance.

The diagram below was originally designed for legacy controllers operating on the RS-485 line, but it can also be applied to the U-PROX IP400.

1. Wiring Between Controllers:
   • Wire 1 – connects all resistors within the blocking zone.
     At its first end, it is joined with Wire 2 (on the last controller, it connects only to the resistor);
     the other end remains unconnected.
   • Wire 2 – connects all blocking magnetic contacts (MCs) on each door in series;
     the second end is connected to the common ground (GND).
   • Wire 3 – connects the GND terminals of all controllers together.
2. Purpose:
   • Originally designed for RS-485-based NDC-F18 devices, this wiring scheme can be easily adapted for other controllers, including U-PROX IP400.
3. Logic of Operation:
   • When a door is opened, its magnetic contact (MC) closes the circuit, causing the corresponding zone to change its state to “blocking.”
     However, for this particular door, it has no effect — since it is already open.
   • All other doors will remain in the “blocked” state and cannot be opened with regular access cards — only cards assigned with the “security service” attribute can override this block and gain access.