What This Article Covers -- and Who It Helps
When a door is controlled by an access control system, every legitimate exit has to be explained to that system. If someone pushes the panic bar and the system does not know about it, an alarm fires, an audit log flags a forced entry, or a mag-lock fails to release in time. The request-to-exit (REX) signal from an exit device is what prevents all of that. This article explains what that built-in switch does, how it differs from a wall-mounted REX device, what the wiring path looks like, and what to confirm before you close the opening. It is written for commercial subcontractors, access control integrators, and facility managers who are either speccing a new opening or troubleshooting an existing one.
What Is a Request-to-Exit Signal from an Exit Device?
A request-to-exit (REX) signal is a dry-contact output that tells the access control panel: a valid exit is happening on this door right now. When the signal arrives, the panel suppresses the forced-door alarm, releases any electric locking device (such as an electrified strike or mag-lock), and starts the door-open timer.
Most people associate REX with a passive infrared (PIR) ceiling sensor or a push button on the wall near the door. Those are standalone REX devices. What is less understood is that many panic bars and exit devices can generate the same signal themselves -- from a switch built directly into the touchbar rail. When someone presses the bar to exit, the switch changes state and the signal goes to the panel before the latch even clears the strike. That sequence matters.
Built-In vs. Separate REX: Why the Distinction Matters on the Job
A wall-mounted PIR or push-button REX is a separate component with its own mounting, wiring, and potential failure point. A signal switch built into the exit device rail eliminates that component -- and gives you a more precise trigger, because it activates only when the bar is actually pressed, not when someone walks near the door.
- PIR REX (ceiling or wall): Hands-free, good for healthcare corridors and assisted-living where staff carry supplies. Can generate false activations if aimed at a high-traffic area.
- Push-button REX: Deliberate activation, reduces nuisance alarms, but requires a free hand and adds a device to coordinate.
- Signal switch in exit device rail: Activates precisely when the touchbar is depressed. No separate device needed. Output wires route through the door via an electric hinge or door cord (power transfer) to the access control panel.
For openings where the exit device is already the primary hardware -- schools, industrial facilities, retail back-of-house, hospital stairwells -- the built-in switch is often the cleanest solution.
How the Signal Gets Off the Door
The switch lives in the rail of the exit device. Getting its output wires from the door (a moving leaf) to the frame (where conduit runs to the panel) requires a transfer path. The two common methods are:
- Electric hinge (power transfer hinge): Wires run through a hinge that has conductors built into the knuckle. The hinge manufacturer and exit device manufacturer must be matched for conductor count. For example, a standard REX-only switch requires a lower conductor count than a combination of electric latch retraction plus REX plus latchbolt monitor.
- Door cord (looped power transfer): A flexible wire loop is surface-mounted at the top of the door and frame. Higher conductor capacity, easier to retrofit, more visible.
Always check the manufacturer's wire gauge chart before you finalize the hinge spec. The required AWG and conductor count vary by the combination of electrified options on the device. Undersizing the conductor is a common field mistake that shows up as intermittent signal dropout.
Wiring the Signal at the Panel: NO, NC, and Common
The REX switch in an exit device rail is a dry-contact switch -- it has no power of its own. It provides three terminals: Common (C), Normally Open (NO), and Normally Closed (NC). The access control panel input determines which terminal pair you use.
- Normally Open (NO) to Common: Circuit closes when bar is pressed. Panel sees a closed loop as the REX trigger. Most common configuration.
- Normally Closed (NC) to Common: Circuit opens when bar is pressed. Used when the panel is configured to monitor line supervision or when the integrator prefers a fail-active approach.
Confirm with the access control integrator which terminal pair the panel expects before you pull wire. Wiring to the wrong pair means the REX fires constantly or never fires -- neither is acceptable.
Wire Colors: Match the Device Leads, Not the Hinge Harness
One field gotcha worth calling out explicitly: the wire colors coming out of the exit device do not necessarily match the wire colors in the electric hinge harness. Each manufacturer uses its own color scheme. When using an ElectroLynx-style connector system, the installer must map exit device lead colors to hinge pin positions per the device-specific wiring diagram -- not by color alone. Skipping this step is how C, NO, and NC get crossed at the connector and the system behaves erratically.
REX Signal vs. Electric Latch Retraction: Two Different Jobs
A REX signal and electric latch retraction (ELR) are sometimes confused because they can exist on the same exit device. They do different things:
- REX signal (switch option): A passive output that tells the panel an exit is happening. The latch is still released mechanically by pushing the bar -- the signal is just informational.
- Electric latch retraction (ELR): The panel (or a timer) sends power to the device to retract the latchbolt electrically, allowing the door to open by push or pull without pressing the bar. Used for automatic door openers, delayed egress coordination, or remote release.
Some openings need both: ELR for remote or automatic release, plus a REX switch to tell the panel when a manual egress has occurred. When both options are on one device, the conductor count at the hinge increases -- confirm the hinge spec covers it before the door is prepped.
Applications Where This Combination Is Specified Most Often
- K-12 schools and universities: Stairwell doors and exterior exit doors with access control need REX to prevent alarm fatigue from normal egress traffic during class changes.
- Healthcare: Corridor doors with mag-locks must release cleanly on egress. A bar-mounted switch provides a code-compliant, hands-free-adjacent egress signal without relying on a PIR that could be blocked by equipment.
- Industrial and warehouse: Shipping dock and production exit doors where workers carry loads and cannot press a wall button benefit from a switch triggered by the bar itself.
- Retail and mixed-use: Back-of-house doors with access control on the entry side. REX from the exit device keeps audit trails clean and prevents false forced-entry alerts.
Preferred Exit Devices for REX-Equipped Openings
DoorwaysPlus.com carries exit devices from Sargent and Corbin Russwin with factory-available signal switch options -- designated in their option codes as the 55- prefix (Sargent) and M92 option (Corbin Russwin). The Rockwood PDU8500 panic device also carries a REX wiring option using the same ElectroLynx connector system. These lines offer stable, service-friendly architectures where switch kits can be retrofitted into an existing rail without replacing the entire device body -- a practical advantage when a facility manager needs to add access control to a door that was originally installed as a purely mechanical exit.
If you are sourcing electric hinges to carry the signal wires, Hager and McKinney electric hinges are compatible with these device families. Confirm conductor count against the specific option combination before ordering.
Before You Close the Opening: a Short Checklist
- Confirm switch option is ordered at the factory (retrofit kits exist but require disassembly of the rail)
- Verify electric hinge or door cord conductor count matches the total electrified options on the device
- Map wire colors from device leads to hinge harness using the device-specific diagram -- do not rely on color matching alone
- Confirm with integrator whether panel input expects NO or NC
- Test the signal path at the panel before the door is put into service: press the bar, confirm the panel logs an exit event and suppresses any alarm
- Document the wiring diagram in the project closeout package for the facility manager
Get the Right Hardware for Your Access Control Opening
If you are specifying or sourcing an exit device with a built-in REX switch, the DoorwaysPlus team can help you match the device option, the compatible electric hinge, and the power transfer method to your opening in one conversation. Browse exit devices and electrified hardware at DoorwaysPlus.com or contact us directly for a project quote.