A fall detection radar is built to answer one question: has the person in this room ended up on the floor when they should not be. In a bathroom, that question has a clear answer, because the only normal postures are standing and sitting. In a bedroom, the same question has the opposite answer, because lying down is the normal state for most of the night.
Those two rooms need opposite logic, so this radar ships in two versions: a bathroom version and a bedroom version. They are not interchangeable, and using the wrong one produces either false alarms or missed events.
This article explains what each version is tuned for, why the two cannot be merged into one, and how to choose.
Why These Two Scenes, and Only These Two
A public area can be covered by a camera and by staff. A bedroom and a bathroom cannot, and those are precisely the two rooms where an elderly person is most likely to be alone and most likely to fall.
So the problem is not "detect falls everywhere". It is "detect falls in the two rooms where a camera cannot go and where nobody is watching". Both of those rooms are small, enclosed, and have a predictable layout. That is what makes radar-based sensing practical in them.
It is also what makes them different from each other.
The Bathroom Version: One Door, Known Path
A bathroom has no bed. The normal postures are standing and sitting, and anything lower is a problem. That gives the bathroom version a simple rule: a low posture is an event.
The version watches for four conditions:
| Condition | What It Means |
|---|---|
| Lying down | The person is on the floor |
| Sitting down and not getting up | A collapse onto the toilet or the floor |
| No movement for a prolonged period | The person has stopped moving entirely |
| In the room for too long | The person has not left within the expected time |
Any one of these raises an alarm.
What makes this reliable is the door. A bathroom has one, and the person enters and leaves through the same one. The radar therefore knows when someone arrived, and knows when the room is empty. That single fact resolves most of the interference in the room: a washing machine, a flushing toilet, or a shower curtain settling after the person has gone can all be discarded, because the radar already knows nobody is inside.
The height and movement-amplitude measurements that radar provides natively do the rest. A tall target becomes a wide, low target, and that transition is the fall.
The Bedroom Version: Inside the Bed vs Outside the Bed
A bedroom has a bed, and that changes everything. Lying down is the normal state for eight hours a night. A radar that treated a low posture as an event would alarm continuously from the moment the person got into bed.
So the bedroom version inverts the rule: inside the bed is normal, outside the bed is an event.
The bed, and any sofa or low platform in the room, is excluded from the monitored zone. Everything else in the room is monitored in full. A person who gets out of bed and collapses on the floor, slips while standing beside the bed, or falls against a wardrobe is detected immediately. The same person turning over, sitting up, or lying still in bed produces nothing.
This is the distinction the bathroom version does not need to make. A bathroom has no bed, so nothing has to be carved out. A bedroom has one, and failing to carve it out would make the product unusable.
Why the Two Cannot Be Merged
The two versions need opposite conclusions from the same measurement.
| Bathroom Version | Bedroom Version | |
|---|---|---|
| Low posture | An event, reported | Normal inside the bed, ignored |
| Long stillness | An event, reported | Normal inside the bed, ignored |
| Key structural feature | The single door | The bed |
| Zone that must be excluded | Interference sources | The bed and any low furniture |
| Detection area and zone precision | Tuned for a small wet room | Tuned for a bed plus its surroundings |
A single set of parameters cannot satisfy both. Tune it for the bathroom and it alarms all night in a bedroom. Tune it for the bedroom and it misses a collapse on a bathroom floor. The height signal is identical in both rooms; the required answer is opposite.
This is why the product ships as two versions rather than one version with a mode switch, and why the difference is not a firmware setting that a user can change.
Zero Configuration
Neither version requires the user to mark anything.
The user does not define the bed position, the door position, the room boundary, or the monitored zone. Each version ships with its zone logic already configured for the scene it is built for. Mount it, power it on, and it is working.
That is deliberate. Asking a user to draw a bed outline on a floor plan introduces two failure modes at once: the setup is difficult for the people most likely to buy this product, and an incorrectly drawn zone silently removes the protection they paid for. A zone that is drawn slightly too small is worse than no zone at all, because it looks like it is working.
Both versions are configured at the factory for the scene they serve. The only thing the user chooses is which room the radar is going into.
What Happens If You Use the Wrong Version
The two failure modes are symmetric, and both are predictable.
Bathroom version installed in a bedroom. The radar has not been told that a bed exists, so a person lying in bed is a low posture that persists. The result is a fall alarm within minutes of the person going to sleep, repeated every time they turn over. In a room with a tatami platform or a floor mattress, the same thing happens the moment someone lies down to rest.
Bedroom version installed in a bathroom. The radar has been configured to ignore low, persistent targets inside an excluded zone. A person who sits down on the toilet and does not get up, or who collapses and stays down, may fall inside that excluded logic and never be reported.
Neither behaviour is a defect. Both are the direct consequence of asking one version to work in the room the other version was built for.
Which Version Do You Need
- Installing in a bathroom, shower room, or toilet — use the bathroom version.
- Installing in a bedroom, to monitor someone getting out of bed — use the bedroom version.
- Covering both rooms — order one of each. They are separate units for separate rooms, and one unit cannot serve both.
- Installing anywhere else — this radar is not the right product. For corridors, living rooms, and open spaces, use a presence radar instead.
- Not sure which room your installation matches — describe the room, or send a photo and the room dimensions, before ordering. It takes a message and prevents a return.
The short version: the bathroom version goes in the room with a toilet, and the bedroom version goes in the room with a bed.
What Neither Version Does
- Neither is a medical device or an emergency service. Both publish alarms to your MQTT broker. Delivering a notification to a person is done by your own system.
- Neither achieves a zero missed-event rate. The design target is the highest practical reporting rate in the intended scene. No sensor of this type eliminates missed events.
- Neither eliminates false alarms. Tuning reduces them. The scene is what removes most of them.
- Neither replaces human checks. For anyone at real risk, this is an addition to a care routine, not a substitute for one.
- Neither works in an open space. Both are specified for a small enclosed room.
- A tatami platform, a floor mattress, or a low bed needs a conversation first. If the sleeping surface is at floor level, tell us before ordering so the right version and the right mounting position can be confirmed.
Summary
A fall detection radar has to decide whether a low posture is normal. In a bathroom it never is, so the bathroom version reports it immediately and uses the single door to know when the room is empty. In a bedroom it usually is, so the bedroom version excludes the bed and monitors everything outside it.
Those are opposite requirements, which is why the product ships in two versions, why the zone logic is fixed at the factory, and why the user never has to mark anything.
Choose by room: the bathroom version for the room with a toilet, the bedroom version for the room with a bed. Using the wrong one produces either an alarm every time the person lies down, or no alarm at all when they fall.
Further detail on the alarm fields, timing parameters, and MQTT properties is in the companion article The Fall Detection Radar: How Alarms Work, How to Tune Them, and What to Expect.
