Installing a Request-To-Exit (REX) Sensor on the DC20

Topics included in this article:

• What is a REX sensor?
• Product notes
• Installation Diagrams
  • Supervision
• Supervised vs Unsupervised
• Settings in Rhombus Console
• Helpful Links
• Contact Support or Sales

What is a REX sensor?

A REX device is any sensor that conveys an intent to leave a secure area by egress through a controlled door.

A REX is required for all electromagnetic lock installations to facilitate the release of the lock for egress. With other locking hardware, such as an electrified strike, a REX can also be leveraged to differentiate normal egress (e.g., using a crash bar or handle to mechanically retract a latch) from a keyed or forced entry. The sensor type compatible with the DC20 is a "contact-type device with a NO or NC state."

Example: Motion sensors, push (crash) bars, push buttons, touchless, etc.

Product Notes:

• Up to four REX sensors can be connected to the DC20.
• Wire type and size: solid or stranded, minimum 24 AWG with a maximum run length of 300 ft.
• Final configuration will be done via the Rhombus console.
• Example use cases for REX sensors:
  • Used as push buttons on walls to release locks.
  • Integrated into existing panic/crash bars.
  • Embedded into PIR sensors above door frames (like automatic doors at supermarkets).

Installation Diagrams

Note: Ensure the installation meets the related safety requirements in your area.

REX Sensors can be installed with or without Supervision. 

Supervision

A supervised circuit has additional resistors strategically placed to detect a fault, usually a cut or a short, between the resistor and the DC20. The standard supervised circuit requires 4.7 kΩ resistors and should be located as close to the sensor as possible. These have been provided with the DC20. 

Rhombus recommends Double EOL on all REX and DPI installed with Rhombus access control. When configured as supervised, the input circuit will report both open and closed and open circuit, shorted, and foreign voltage.

For double EOL supervision, the series resistor should always be between the DC20 and the parallel resistor. Failing to do so may result in a "foreign voltage" error.

Supervised vs Unsupervised

A supervised circuit has additional resistors strategically placed to detect a fault, usually a cut or a short, between the resistor and the DC20. A supervised input circuit requires two resistors to facilitate proper reporting.

An unsupervised circuit will only report open or closed. It will not report an open circuit, a shorted circuit, or foreign voltage. 

Settings in Rhombus Console

After installing the REX you will need to set up the options of Normally open, Normally Closed, Unsupervised and Supervised in the Rhombus console. 

1. Navigate to "Settings," click "Door Controllers," and then select the Door Controller to which the REX sensor is connected.

2. In the "Rex Port" section, select "Configure" or "Edit" if adjusting an already added Rex sensor.

3. Set the "Normal State" to align with the wiring of the Rex sensor, either Normally Open (NO) or Normally Closed (NC) configuration.  If the Rex is behaving the opposite of the expected behavior, swapping this configuration in the console can oftentimes resolve the issue.

4. Configure the "Port Type" to either a Supervised or Unsupervised circuit.

5. Click "Save" or "Create."

Helpful Links

• Installing/Registering the DC20
• DC20 Overview
• Setting up Access Control Door in Rhombus Console

Contact Support or Sales

Have more questions? Contact Rhombus Support at +1 (877) 746-6797 option 2 or support@rhombus.com.

Interested in learning more? Contact Rhombus Sales at +1 (877) 746-6797 option 1 or sales@rhombus.com.