NXT-MSC 2D/4D Controller Hardware Installation Guide

NXT-MSC 2D/4D Controller Hardware Installation Guide

1.0 Introduction

This document contains basic information for the installation of the NXT-MSC 2D and 4D controllers.

2.0 Important Note:  

Keri Public Statement on the Amazon Key 

Keri does not support the use of the Amazon Key on Keri controllers. The Amazon Key does not interface to Keri products in a way that allows the Building Owner or Manager to maintain complete control over their system, nor does it provide any tracking information on when the Amazon Key was used to open a door. The addition of the Amazon Key to a site introduces a security degradation beyond the control of Keri's access control system.

Neither Keri nor Amazon provides any documentation on how an installer would integrate the Amazon Key with Keri's access control system. Because of this, Keri has strong concerns about the knowledge of the Amazon Key installers as evidenced by the damage Amazon Key installers have caused to Keri controllers and installations at multiple sites.  

Any Keri controller failure caused by the installation of an Amazon Key device is cause for voiding the controller warranty.

Keri cannot be held responsible for any security lapses created by the use of the Amazon Key.

3.0 Product Specifications

3.1 Unit Dimensions

• NXT 2D/4D controller PCB
- 6.75 inches high by 6.00 inches wide by 1.75 inches deep, including wiring connectors
- (17.15 cm by 15.25 cm by 4.45 cm)

• Enclosure
- 13 inches high by 9 inches wide by 4 inches deep - (33.02 cm by 22.86 cm by 10.16 cm)

 Operating Temperature/Humidity Range
- 32°F to 150°F (0°C to 60°C) 
- 0% to 90% Relative Humidity, non-condensing

3.2 Controller Power Requirements

Input Power
• 10 to 14 VDC @ 2.5 A (maximum current draw for a fully loaded NXT-2D/-4D controller)

Output Relay Contact Rating
• 1 Amp @ 24 VDC

Current Draw Requirements as 12VDC
 • 650 mA max for an NXT-4D Controller
• 570 mA max for an NXT-2D Controller
• 210 mA max for each NXT-4x4
• 85 mA max for each NXT-1R, NXT-3R, NXT-4R, or NXT-5R Reader
• 115 mA max for each NXT-6RK Reader
• 50 mA max for each NXT-RM Reader Interface Module

Note: Keri recommends using separate, linear power supplies for the controller and the electronic locking device (magnetic lock, door strike, etc.). Should you decide to use the same linear power supply for both the controller and the electronic locking device, ensure the linear power supply provides enough current to drive the controller, the locking device, and any peripherals that may be connected (i.e., reader, 4x4, RIM), including an adequate safety margin.

3.3 Input Device Configuration - 3 Inputs

• Door Sense - normally closed
• Request to Exit - normally open
• Global Unlock - normally open,
   or Auxiliary RTE A-Door - normally open

3.4 Controller Memory Retention

• 5 year lithium battery back up to support controller RAM and real-time clock

3.5 Buffer Capacity

  1. Up to 200,000 Cardholders
  2. 10,000 Events

3.6 Reader Capacity

NXT2D Controller

  1. 4 with NXT Readers *
  2. 2 with Wiegand or MS Readers
* 4 Reader capacity requires the Mercury Firmware option and two NXT Exit Readers

NXT4D Controller

  1. 8 with NXT Readers *
  2. 4 with Wiegand or MS Readers
* 8 Reader capacity requires the Mercury Firmware option and four NXT Readers

4.0 NXT Wiring Diagrams

4.1 NXT 2D/4D Controller Wiring Diagrams

See the table in section 4.0 for LED definitions.

Note: This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a residential area may cause harmful interference in which case the owner will be required to correct the interference at the owner’s expense.

4.2 Wiring a Fail-Safe Lock

4.3 Wiring a Fail-Secure Lock

4.4 Lock Port Protection

Transorbs are provided with the controller ship kit. They are used to protect the controller from voltage spikes induced on the port wiring by absorbing the excess voltage and slowly releasing it back into the circuit. Keri strongly recommends wiring in the transorbs provided with the controller ship kit. Refer to the Transorb Wiring Diagram below.

Note: The Transorbs that Keri provides are non-polar; they can be installed in either orientation.

4.5 Using Isolation Relays

For locking devices that may induce heavy voltage spikes – Mag Locks and devices with heavy-duty solenoids such as turnstiles, vehicle gates, and overhead doors – Keri recommends using isolation relays. Keri has an Isolation Relay Kit (p/n IRP-1). Please refer to the IRP-1 Isolation Relay Installation Guide (p/n 01833-001) for detailed information.

5.0 Controller LED Definitions

6.0 Wiring Instructions

6.1 Terminal Blocks

PXL Wiring Instructions

Note: Screws on terminal blocks must be tightened securely.

6.2 Connecting the Earth-Ground and the 12VDC Power 

Power wiring

6.3 Controller Earth-Grounding

To ensure optimum earth-grounding of the controller and its connected peripherals, you should make a quality earth-ground connection to the metal enclosure lug (which displays an adjacent earth-ground symbol).

This good-quality earth-ground at the enclosure lug will provide an earth-ground for the entire enclosure - and will therefore ground anything that is connected to the metal enclosure - (the four metal screws at each corner of the PCB) - plus, through circuitry on the PCB, this includes anything connected to the lug marked J6 or pin 3 of the TB10 power connector.

In addition, the enclosure itself must be earth grounded to a good quality ground point external to the enclosure for a complete path to ground.

Also, the shield/drain wire of any reader/peripheral cables MUST be terminated to one of the following points-any corner screw attaching the controller to the enclosure, Pin 3 of TB10, the green ground lug (J6) on the controller, or the ground lug of the enclosure.  Failure to properly earth ground the reader/peripheral drain wire may result in unreliable communication or operation of the attached peripheral.

7.0 Cable Requirements

  1. Cable resistance causes a drop in voltage at the end of long cable runs. Ensure the appropriate power and current for your device is available at the device at the end of the cable run. Heavier gauge cable reduces this effect.
  2. Keri does not recommend hot-plugging a Reader, RIM, or 4x4 into an NXT controller. Remove power from the controller prior to connecting these devices

7.1 RS-485 Cable Requirements

RS-485 bus runs can daisy-chain together an NXT-4x4 and NXT-Reader on one line. The total cable run distance should be no more than 500 feet from the NXT controller for runs with 4x4s and no more than 1,000 feet for Reader-only runs.

Recommended RS-485 Cable Types


Run Length





Twisted Pair


RS-485 from NXT-MSC controller to NXT 4x4 (with or without an NXT 1R/3R/5R reader)

Up to 500 feet (150 meters)








22 or 24

RS-485 from NXT-MSC controller to NXT 1R/3R/5R readers

Up to 1,000 feet (300 meters)








22 or 24

Controller Power, Inputs, and Outputs Cable Requirements

Total Run Length
# of Conductors
Controller Power
250 feet [a]
Earth Ground
Shortest path [b]
Inputs and Outputs [C]
500 feet
  1. To meet CE and C-tick regulations, the length of the controller power line can be no longer than 3 Meters (9.85 feet).
  2. Use the shortest possible path from earth ground point to PCB. Connect the earth ground only to the designated pin on the terminal block. This is important as all transient protection for the unit is made through this earth ground connection. For unit protection, the earth ground connection should always be made first.
  3. Values listed are minimums. Individual input and output devices may have more specific requirements.

  1. The Lock Output relay may require a heavier gauge of wire depending upon the current demands of the lock and the length of the lock wiring run.
  2. Cable resistance causes a drop in voltage at the end of long cable runs. Ensure the appropriate power and current for your device is available at the device at the end of the cable run. Heavier gauge cable reduces this effect.
  3. Keri does not recommend hot-plugging a Reader, RIM, or 4x4 into an NXT controller. Remove power from the controller prior to connecting these devices.

7.2 Earth-Ground Cable Requirements

  1. Single conductor, AWG 18 wire (or a larger gauge).  Ground wire is green with or without yellow tracer.

7.3 Keri Systems Proximity Readers

  1. six conductor, shielded, stranded, AWG 24 wire (Belden 9536 or a larger gauge).
  2. four conductor, shielded, stranded, AWG 24 wire (Belden 9534 or a larger gauge) for the MS-4000 only (there is no beeper or LED in the MS-4000).

7.4 Wiegand Compatible Readers

  1. four to seven conductor, shielded, stranded, wire – depending upon the Wiegand reader’s requirements.
  2. a minimum gauge of AWG 24 is required for data transfer with a 500-foot maximum run length per Wiegand specification.

7.5 Keri NXT Readers

  • NXT reader extension cable type is: Belden 9841 or equivalent (one twisted pair) for data combined with Belden 8461 or equivalent for the 18x2 power cable or Belden 9842 or equivalent (two twisted pairs in one jacket).

8.0 Controller Factory Reset

Keri recommends resetting NXT-MSC controllers the first time these controllers are powered on. 

8.1 Reset an NXT-MSC Controller

Note: Resetting an NXT controller with Mercury firmware will restore the controller to a factory default state. It removes all network configuration data assigned to the controller such as the IP Address, Subnet Mask, and Gateway address. Keri recommends resetting NXT controllers the first time these controllers are powered on.

Perform the following to reset an NXT controller with Mercury Firmware:
  1. Ensure there is a jumper shorting both pins of J3 (next to the white S1 button)
  2. With the controller powered on, press S1 once. 
  3. Power the controller off (while the DMODE LED is solid green).
  4. Release the S1 button and the reset process begins. This takes about 20 seconds.
  5. The reset process is complete when LED “d” (D48) starts blinking about once a second.

9.0  Back-Door Web Browser Access

When an end user enters the web browser configuration interface and changes the password from the default to a unique value, the default password is disabled. Should the unique password be lost, the user is locked out of the web browser. The new firmware provides a temporary window of access for the web browser, provided you can access the controller itself. This access method is available in controllers with firmware v1.01.40 and greater.

On the controller, press S1 twice to start a five minute window in which the default password is enabled allowing the web browser to access that controller. After five minutes the default password is disabled and the unique password is enabled.

Keep in mind, a hardware reset will restore the factory default web browser password, as well as reset the controller to factory default values.

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