The dual door interface board enables OEM system integrators to connect TTL (D1/D0, Clock/Data), F/2F, 2-wire RS-485 devices, and door hardware. It includes:

• Support for tri-state LED control and buzzer control

• Six Form-C relay outputs for strike control or alarm signaling

• Eight supervised or unsupervised inputs for door position, request to exit push button, and alarm contact monitoring

• 2-wire RS-485 communication with the system controller.

Dual Door Interface Components

Supplying Power to the Dual Door Interface

The dual door interface accepts 12 to 24 V DC for power on TB7 (VIN and GND).

• Locate the power source as close to the MR52-S4 as possible.

• Use a minimum of 18 AWG wire.

• The VOUT terminal on TB7 provides the same voltage as VIN.

Communication Wiring (SIO Communication Port)

The dual door interface communicates with a controller over a 2-wire RS-485 interface, supporting multi-drop communication on a bus of up to 4,000 feet (1,200 m).
Use a twisted-pair cable (minimum 24 AWG) with drain wire and shield. See dual door interface specifications.

Reader Wiring

Each reader port supports a reader with TTL (D1/D0, Clock/Data) or 2-wire RS-485 signaling. Use the following cable types:

• TTL (Wiegand): 6-conductor (18 AWG).

• RS-485: 4-conductor twisted pair (24 AWG, 120Ω, shielded). Use one pair for data and one pair for power.

Power to the reader is 12 V DC, 600 mA maximum per reader port. Readers that require different voltage or have high current requirements must be powered separately with a common ground. Refer to the reader manufacturer specifications for cabling requirements. In the 2-wire LED mode the buzzer output drives the second LED. Reader port configuration is set via the host software.

JP8 and JP9 OSDP Termination Jumpers

The JP8 (reader port 1) and JP9 (reader port 2) jumpers control OSDP termination and are located just below the GND pins of each reader port (with the reader ports oriented at the top). Set the jumper to the ON position when using an OSDP reader. Set the jumper to the OFF position when using a non-OSDP reader.

Reader Wiring Diagrams

Alarm Contact Wiring

There are eight inputs that are typically used to monitor door position, request to exit or alarm contacts. Input circuits can be configured as:

• Unsupervised (2 states): Reporting as open or closed contact.

• Supervised (6 states): Reporting as open or closed contact, open circuit, shorted circuit, grounded circuit*, or foreign voltage*.
  (*Grounded and foreign voltage states are not a requirement of UL 294 and therefore not verified by UL.)

By default, inputs configured as supervised require two 1 kΩ, 1% resistors installed as close to the sensor as possible to ensure proper circuit supervision. Custom end-of-line (EOL) resistances can be configured via the host software.

Inputs for Cabinet Tamper/Power Fault

Input TMP and input FLT are used for monitoring cabinet tamper and power failure with normally closed contacts. These two inputs are for contact closure monitoring only, and do not use EOL resistor(s).

Control Output Wiring

The dual door interface provides six Form-C relay contacts for controlling door strikes or other connected devices. When switching loads, especially inductive loads such as strikes, abnormal contact wear and premature contact failure can occur. Inductive loads can also generate electromagnetic interference (EMI), which may affect the operation of nearby equipment.

To improve reliability and extend relay life, always install a contact protection circuit. The circuit should be placed as close to the load as possible (within 12 inches [30 cm]). Installing it farther from the load reduces its effectiveness. Use wire gauges that are appropriately sized for the load current to prevent voltage loss.

Diode selection

• Diode current rating > 1x strike current

• Diode break down voltage: > 4x strike voltage

• For 12 V DC or 24 V DC strike, diode 1N4002 (100V/1A) typical

Address and Baud Rate

DIP Switches 1 to 5 set the device address. Switches 6 and 7 set the communication baud rate. All other configuration settings are set via host software.

* DIP switch 8 (S8) is reserved and not used.

Factory Reset

While not normally required, it is possible to perform a factory reset of the dual door interface, which deletes all onboard stored data. To perform the delete:

1. Set all DIP switches to OFF.

2. Remove power from the dual door interface.

3. Restore power to the dual door interface.

4. Within 3 seconds, toggle DIP switch 8 ON.

Status LEDs

Power-up

All LEDs are OFF.

Initialization

Once power is applied, initialization of the module begins.

When initialization is completed, LEDs A through R2 are briefly sequenced ON then OFF.

Run Time

After the above sequence, the LEDs have the following meanings:

Specifications

Revision D assembly:

The Interface is for use in low voltage, class 2 circuits only.

The installation of this device must comply with all local fire and electrical codes.

• Primary power: 12 to 24 V DC ± 10%, 550 mA maximum (reader current not included)

• Outputs: Six Form-C relays: 

  • Normally open contact (NO) contact: 5 A @ 30 V DC resistive

  • Normally closed contact (NC) contact: 3 A @ 30 V DC resistive

• Inputs:

  • Eight unsupervised/supervised, standard EOL: 1k/1kΩ, 1%, ¼ watt

  • Two unsupervised, dedicated for cabinet tamper and UPS fault monitoring

• Reader interface:

  • Power: 12 V DC, 600 mA maximum each reader port

  • Data inputs: TTL (Wiegand) compatible or 2-wire RS-485

  • LED output: TTL compatible, high > 3 V, low < 0.5 V, 5 mA source/sink maximum

  • Buzzer output: Open collector, 12 V DC open circuit maximum, 40 mA sink maximum

  • Communication: 2-wire RS-485: 38400, 115200 bps

• Cable requirements (all ports shall use shielded conductors):

  • Power: One twisted pair, 18 AWG

  • RS-485 I/O devices: One twisted pair with drain wire and shield, 24 AWG, 120Ω impedance, 4,000 feet (1,200 m) maximum

  • Alarm inputs: One twisted pair per input, 30Ω maximum

  • Outputs: As required for the load

  • Reader data (TTL): 6-conductor, 18 AWG, 500 feet (150 m) maximum

  • Reader data (RS-485): One twisted pair with drain wire and shield, 24 AWG, 120Ω impedance, 2,000 feet (610 m) maximum

• Mechanical:

  • Dimension: 6 inches (152 mm) W x 8 inches (203 mm) L x 1 inch (25.4 mm) H

  • Weight: 9.5 oz. (270 g) nominal

• Environmental:

  • Temperature:

    • Storage: -55 to +85°C

    • Operating: 0 to +70°C

  • Humidity: 5 to 95% RHNC

Performance Levels

Evaluated to UL 294 8th edition and ULC 60839-11-1: Grade 2 and indoor dry.

Optional requirements of ULC 60839-11-1 items have not been evaluated.

These specifications are subject to change without notice.

Liability

The Interface should only be used to control exits from areas where an alternative method for exit is available. Thisproduct is not intended for, nor is rated for operation in life-critical control applications. LenelS2 is not liable under any circumstances for loss or damage caused by or partially caused by the misapplication or malfunction of the product. LenelS2’s liability does not extend beyond the purchase price of the product.

Regulatory

This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

The dual door interface board must be powered by an NRTL (Nationally Recognized Testing Laboratory) approved by Class 2 Listed Power Supply. Expansion port and supervised input functionality were not evaluated by UL.

_{© 2026 Honeywell International Inc. All Rights Reserved.}