2.0 Product Specifications
2.1 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)
- 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
2.2 Controller Power Requirements
• 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.
2.3 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
2.4 Controller Memory Retention
• 5 year lithium battery back up to support controller RAM and real-time clock
2.5 Buffer Capacity
- Up to 200,000 Cardholders
- 10,000 Events
2.6 Reader Capacity
2.1 NXT2D Controller
- 4 with NXT Readers *
- 2 with Wiegand or MS Readers
* 4 Reader capacity requires the Mercury Firmware option and two NXT Exit Readers
2.1 NXT4D Controller
- 8 with NXT Readers *
- 4 with Wiegand or MS Readers
* 8 Reader capacity requires the Mercury Firmware option and four NXT Readers
3.0 NXT Wiring Diagrams
3.1 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.
3.2 Wiring a Fail-Safe Lock
3.3 Wiring a Fail-Secure Lock
3.4 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.
3.5 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.
4.0 Controller LED Definitions
5.0 Wiring Instructions
5.1 Terminal Blocks
Note: Screws on terminal blocks must be tightened securely.
5.2 Connecting the Earth-Ground and the 12VDC Power
Note: TB2 is colored red to make it easier to tell it apart from the network connector
5.3 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.
6.0 Cable Requirements
- 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.
- 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
6.1 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
Controller Power, Inputs, and Outputs Cable Requirements
Total Run Length
# of Conductors
250 feet [a]
Shortest path [b]
Inputs and Outputs [C]
- To meet CE and C-tick regulations, the length of the controller power line can be no longer than
3 Meters (9.85 feet).
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.
- Values listed are minimums. Individual input and output devices may have more specific