Key takeaways
- A REX device signals that someone is leaving. It is an input to a lock circuit or a controller, not the lock itself.
- Von Duprin's catalog says the device is equipped with one internal SPDT switch which monitors the push pad. Von Duprin's catalog says it should not be used to control a load.
- On Securitron's XMS2, never switch the magnetic lock through the REX relay contact; wire its lock-control output instead. On the DS160/161, the relay can release the lock, and Bosch names a diode or bridge rectifier for a relay without spike protection.
- Whether a sensor-only release is acceptable at a given door is decided by the adopted code and the authority having jurisdiction, not by the sensor's data sheet.
The role
What does a request-to-exit device actually do?
A REX device is the input that says a person is leaving. On the DS160/161, when the sensor sees motion, power is removed from the magnetic lock. Securitron's XMS2 is designed to release a magnetic lock from the inside of an opening for free egress.
The egress rules that decide how a door must release, and the five release paths a maglock opening has to prove, are covered inmaglock release and egress requirements. Read that page first if the question is what the door is allowed to do rather than which device to mount.
Types
What are the main types of REX device?
| Family | Example from the sheets | What the sheet specifies |
|---|---|---|
| PIR motion sensor | Bosch DS160/DS161; Securitron XMS2; Optex OP-08C | Mounted above the door. Bosch: ceiling or wall mounting up to 15 ft (4.6 m). Optex: header, transom or ceiling up to 13 feet. Securitron: indoor use only. |
| Push button | dormakaba RCI 906 and RCI 908 | Single-gang surface or recessed box mounting. A 1-9/16 in. button in red, black or green. Momentary, maintained or time-delay switches. |
| Exit-device switch | Von Duprin 98/99 RX option | One internal SPDT switch monitoring the push pad. Intended as a signalling switch, with a low-current (LC) version rated 50ma max. |
| Touch-free actuator | dormakaba RCI 913 microwave switch; RCI 912-WBT | RCI 913 pattern depth adjustable from 4 in. to 24 in. RCI 912-WBT detection distance adjustable from 3 to 30 cm. |
Motion sensors
Where do motion sensors go on the door?
The DS160/161 sheet says to mount it just above the door, on the hinge side, with the lens pointed down and slightly out.
Above the door, on the hinge side.
On a wall mount with the lens pointed straight down, Bosch notes that some detection zones point at the wall and detect nothing.
Push buttons
How are push buttons chosen and placed?
Both mount to a single-gang surface or recessed electrical box. Dormakaba's sheet lists momentary (2-SPST), maintained (2-SPST) or time-delay (DPDT) switches; confirm the switch type against the lock circuit.
Securitron's XMS2 instructions describe a typical push button located 40-48 inches above the floor and within five feet of the door. That is Securitron's description of its own arrangement. Confirm the mounting position and any required release time with the local building department or fire prevention department, which is what Securitron's own sheet advises.
Exit devices
What is a REX switch inside an exit device?
On a door with exit hardware, the signal can come from the device itself. Von Duprin's catalog says the RX switch option should not be used to control a load.
An RX2 option uses two RX switches, and a WP-RX option is rated to IP67.
Wiring
What do the install sheets warn about when wiring REX devices?
On the XMS2, do not switch the lock through the REX contact.
Securitron's note reads: "Never use the REX relay contact to switch the magnetic lock." The XMS2 has a separate lock-control function, which is fail safe so the magnetic lock releases if power is cut to the detector.
Protect the relay from the lock coil.
The DS160/161 sheet says to use either a bridge rectifier (such as a KBL01) or a diode (such as a 1N4007).
Set the hold time deliberately.
The DS160/161 sheet says the latch time must be set for 16 seconds or greater in order for this to work correctly. Securitron describes a time extension feature so the unit does not reset if a person momentarily stops moving just before the exit.
Match the power to the sheet.
One sheet lists a power supply of 12-24 VAC/DC. Check the range on the exact model's sheet before landing wires.
On site
What should be settled before a REX device is mounted?
- Which family fits the door: a motion sensor above it, a button beside it, or a switch inside the exit device.
- The mounting height against the manufacturer's stated range for the exact model.
- Which side of the door the device is on, and what the coverage pattern will see, including adjacent corridors that call for masking.
- Whether the REX output feeds the lock circuit directly or the controller, and which output on the sensor does which job.
- The switch type or hold time the lock circuit expects.
- Who signs off on the release arrangement at that opening, and what documentation they need.
Questions about request-to-exit devices
Can a REX sensor replace panic hardware?
Not the sensors on this page. The DS160/161 sheet says it is not designed as a primary means of exit for emergency egress applications, and Securitron says the XMS2 shall not impair panic hardware. The release arrangement for the opening is set by the adopted code and the authority having jurisdiction.
How high should a motion sensor be mounted?
It depends on the model. Confirm the range for the exact model and any local requirements with the authority having jurisdiction.
Can the REX relay switch a magnetic lock directly?
It depends on the sensor. On Securitron's XMS2, no: Securitron's note reads, never use the REX relay contact to switch the magnetic lock. On the Bosch DS160/161, when the sensor sees motion, power is removed from the magnetic lock, and Bosch names a diode or bridge rectifier for a relay without spike protection.
Can the switch in an exit device control the lock?
Von Duprin's catalog says the RX switch option should not be used to control a load. Egress and maglock arrangements remain subject to the authority having jurisdiction.
Next step
When does it help to have the opening looked at?
Elwin installs, repairs and replaces request-to-exit sensors and buttons at commercial doors, and configures them with the lock and the controller as one opening. A site walk is the next step to confirm which device the opening needs.
See all before and after photos
Sources and further reading
These sources back up the general guidance. Your building and the people who approve the work decide the details for your doors.
- Bosch Security Systems: DS160/DS161 Installation Guide
- Bosch Security Systems: Intrusion detectors product overview
- Securitron (ASSA ABLOY): XMS2 Exit Motion Sensor Installation Instructions
- Optex: OP-08C product sheet
- dormakaba: RCI Electronic Controls Product Catalog
- Allegion: Von Duprin 98/99 Series Catalog