Lutron Electronics 0079 Occupancy/Vacancy Sensor User Manual 041272b indd

Lutron Electronics Company Inc Occupancy/Vacancy Sensor 041272b indd

Contents

User Manual

2.3
2.4
Key Features
· Low Maintenance. 10-year battery life. Convenient low-battery indicator.
· Multiple Devices. Up to 3 Sensors can work together to control lights for broader coverage
in large spaces. Each Sensor may be added to a maximum of 10 receiving devices.
Sensor Operation
Occupancy Version – The Sensor will automatically turn the lights on when the space is
occupied and automatically turn the lights off after the space is vacated.
Vacancy-Only Version – The lights must be manually turned on* at the dimming or switching
device. The Sensor will automatically turn the lights off after the space is vacated.
* There is a built-in 15-second vacancy grace period that begins when the lights are
automatically turned off, during which the lights will automatically turn back on in response to
motion. This grace period is provided as a safety and convenience feature in the event that the
lights turn off while the room is still occupied, so that the user does not need to manually turn
the lights back on. After
15 seconds, the grace period expires and the lights must be manually turned on.
NOTE: For either Sensor version, the lights can also be manually turned off at any time by
using the dimming or switching device directly.
B
A
Lutron Electronics Co., Inc.
7200 Suter Road
Coopersburg, PA 18036-1299, U.S.A.
Printed in the U.S.A. 07/10 P/N 041-272 Rev. B
Important Notes
1. This Sensor is part of a system and cannot be used to control a load without a
compatible dimming or switching device. Refer to the instruction sheets of the receiving
device(s) for installation information.
2. Clean Sensor with a soft damp cloth only. DO NOT use any chemical cleaners.
3. The Sensor is intended for indoor use only. Operate between 32 °F and 104 °F
(0 °C and 40 °C).
4. DO NOT paint Sensor.
5. Use only high-quality lithium batteries, size CR123, 3 V (ANSI-5018LC, IEC-
CR17345). DO NOT use rechargeable batteries. Using improperly rated batteries could
damage the Sensor.
NOTICE: DO NOT disassemble, crush, puncture, or incinerate batteries. DO NOT
dispose of batteries in normal household waste. Please recycle, take to a proper battery
disposal facility, or contact your local waste disposal provider regarding local restrictions
on the disposal or recycling of batteries.
6. The range and performance of the RF system is highly dependent on a variety of
complex factors such as:
· Distance between system components
· Geometry of the building structure
· Construction of walls separating system components
· Electrical equipment located near system components
WARNING: Entrapment hazard. To avoid the risk of entrapment, serious injury, or death,
these controls must not be used to control equipment which is not visible from every
control location or which could create hazardous situations such as entrapment if operated
accidentally. Examples of such equipment which must not be operated by these controls
include (but are not limited to) motorized gates, garage doors, industrial doors, microwave
ovens, heating pads, etc. It is the installer’s responsibility to ensure that the equipment
being controlled is visible from every control location and that only suitable equipment is
connected to these controls. Failure to do so could result in serious injury or death.
1
2
Removing Temporary Mounting Strip
Remove the Sensor from the mounting bracket by twisting
in a counter-clockwise direction.
If the Sensor coverage and wireless communication tests
have been successfully completed, use the mounting
bracket as a template to mark the screw hole locations
with a pencil.
3.1
Temporary Mounting: Solid Ceiling
Use this procedure if the Sensor will be mounted on a solid, continuous ceiling surface
such as drywall, plaster, concrete, or wood.
One 3M™ Command™ adhesive strip is provided for temporarily mounting and testing
the Sensor on smooth, solid ceiling surfaces. This strip is designed for easy, damage-free
removal and is not reusable. This strip should not be used for permanently mounting the
Sensor (see section G. Permanent Mounting Methods ). Carefully follow the removal
instructions below to ensure the ceiling is not damaged during removal.
NOTE: DO NOT use the adhesive strip on ceiling tiles, as it will likely cause damage to
the tile upon removal.
Peel the red “Command Strips” liner off and apply to the fl at side of the mounting
bracket as shown in the diagram. Press fi rmly.
NOTE: DO NOT cover the bracket’s screw
holes because they will be used to mark screw
hole locations on the ceiling.
NOTE: Leave the removal tab exposed past
the edge of the bracket so it can be accessed
for removal later.
Identify a location on the ceiling where the Sensor will have a good view of the room.
Remove the black “wall side” liner from the adhesive strip.
Position the mounting bracket on
a clean, dry, dust-free ceiling and
press fi rmly for several seconds.
Attach the Sensor to the mounting bracket by inserting and twisting in a clockwise
direction until the Sensor locks into place.
Perform the Sensor coverage and wireless communication tests as described in
sections E. Testing Sensor Coverage and F. Testing Wireless Communication.
2.1
2.2
2.5
2.6
To remove the bracket from the ceiling, grasp the removal tab on the adhesive strip
and pull the tab VERY SLOWLY straight across the ceiling, stretching the strip until
the bracket releases from the ceiling. Discard the strip. NEVER pull the strip at an
angle, as it may break or damage the ceiling surface.
• Easy-to-follow
Instructions
P/N 041-272B
Limited Warranty
(Valid only in U.S.A., Canada, Puerto Rico, and the Caribbean.)
Lutron will, at its option, repair or replace any unit that is defective in materials or manufacture within one year after
purchase. For warranty service, return unit to place of purchase or mail to Lutron at 7200 Suter Rd., Coopersburg, PA
18036-1299, postage pre-paid.
THIS WARRANTY IS IN LIEU OF ALL OTHER EXPRESS WARRANTIES, AND THE IMPLIED WARRANTY OF
MERCHANTABILITY IS LIMITED TO ONE YEAR FROM PURCHASE. THIS WARRANTY DOES NOT COVER THE COST
OF INSTALLATION, REMOVAL OR REINSTALLATION, OR DAMAGE RESULTING FROM MISUSE, ABUSE, OR DAMAGE
FROM IMPROPER WIRING OR INSTALLATION. THIS WARRANTY DOES NOT COVER INCIDENTAL OR CONSEQUENTIAL
DAMAGES. LUTRON’S LIABILITY ON ANY CLAIM FOR DAMAGES ARISING OUT OF OR IN CON NEC TION WITH THE
MANUFACTURE, SALE, INSTALLATION, DELIVERY, OR USE OF THE UNIT SHALL NEVER EXCEED THE PUR CHASE PRICE
OF THE UNIT.
This warranty gives you specifi c legal rights, and you may have other rights which vary from state to state. Some states do
not allow the exclusion or limitation of incidental or consequential damages, or limitation on how long an implied warranty
may last, so the above limitations may not apply to you.
Lutron, Maestro Wireless, and the Sunburst logo are registered trademarks and Radio Powr Savr is a trademark of Lutron
Electronics Co., Inc. ANSI is a registered trademark of the American National Standards Institute. IEC is a trademark of the
International Electrotechnical Commission. 3M and Command are trademarks of 3M Company
© 2010 Lutron Electronics Co., Inc.
Technical Assistance
For questions concerning the installation or operation of this product, call the
Lutron Technical Support Center. Please provide exact model number when calling.
U.S.A. and Canada (24 hrs / 7days)
1.800.523.9466 Fax +1.610.282.6311
Mexico 8am – 8pm ET
+1.888.235.2910
Other countries 8am – 8pm ET
+1.610.282.3800 www.lutron.com
NOTE: Pull very slowly. NOTE: Do not pull at an angle.
English
Radio Powr Savr™
Installation Instructions
Please Read Before Installing Instructions
Wireless Battery-Powered Occupancy and Vacancy Sensors
California Title 24 Compliant
LRF2-OCRB-P 3 V 14 A 434 MHz (Occupancy / Vacancy)
LRF2-VCRB-P 3 V 14 A 434 MHz (Vacancy-Only)
Compatible Products
For a full list of compatible products visit www.lutron.com/occsensors
Product Description
Lutron’s ceiling-mounted Occupancy and Vacancy Sensors are wireless, battery-powered,
passive infrared (PIR) devices that automatically control lights via RF communication with a
dimming or switching device. These Sensors detect the heat from people moving within an
area to determine when the space is occupied. The Sensors then transmit the appropriate
commands to the associated dimming or switching device to turn the lights on or off
automatically, providing both convenience and exceptional energy savings.
Install a Sensor in as
little as 15 minutes
Pre-Installation
Before setting up the Sensor, the corresponding dimming or switching device(s) should
be installed. Refer to that product’s installation sheet for instructions.
Twist and remove mounting bracket to insert battery.
Set-Up
In order for the Sensor to operate properly, it must fi rst be set up with a corresponding
dimming or switching device. The procedure for setting up a Sensor with a Maestro
Wireless® (MRF2-only) Dimmer or Electronic Switch is detailed below.
If setting up a Sensor with a different device, visit www.lutron.com/occsensors or
consult the installation guide for that device for the correct set-up procedure.
Setting up a Sensor with a Maestro Wireless® Dimmer or Electronic Switch
Place the Dimmer or Electronic Switch in
set-up mode by pressing and holding the
tap button for approximately 6 seconds
until all LEDs on the device begin fl ashing.
Release the tap button.
Add the Sensor to the Dimmer or Electronic Switch
by pressing and holding the “Lights Off” button on
the front of the Sensor for approximately 6 seconds
until the lens fl ashes briefl y. The lights in the room will
also fl ash 3 times, indicating the Sensor has been
successfully added. The Dimmer or Electronic Switch
will exit set-up mode automatically.
The “Lights On” and “Lights Off” buttons should now switch the lights in the room on
and off, respectively, when pressed.
Repeat the above procedure to set up the Sensor with any additional devices.
Setting the Occupancy Light Level (Occupancy version, dimming devices
only)
Set the Dimmer to the desired light level for entering the room.
Save the occupancy light level by pressing and holding
the “Lights On” button on the front of a Sensor that has
been set up. After approximately 6 seconds, the lens
will fl ash rapidly several times, indicating the light level
has been saved. All Sensors set up with the Dimmer
will now use the saved occupancy light level.
D
1
2
C Sensor Placement and Coverage
Before mounting the Sensor, please note the following:
• The Sensor is designed for ceiling use only. DO NOT install on ceilings higher than
12 ft (3.7 m) or non-ceiling surfaces. Doing so may signifi cantly inhibit the Sensor’s
performance.
• The Sensor should be installed in a location where it has a good view of all parts of
the room. The Sensor requires line of sight to operate properly. If you cannot see
the Sensor, it cannot see you. The Sensor cannot see through glass objects such
as patio or shower doors.
• DO NOT mount the Sensor within 4 ft (1.2 m) of HVAC vents, within 6 in (15 cm) of
other RF devices, or within 4 ft (1.2 m) of light bulbs installed below the ceiling line.
• The Sensor may be installed up to 60 ft (18.3 m) away from the associated dimming
or switching device(s) if they are in direct line of sight. If there are walls or other
barriers between the Sensor and receiving device(s), the Sensor should be located
within 30 ft (9.1 m).
• Whenever possible, avoid placing the Sensor in a location where it has a broad view
outside the intended space. If this is unavoidable, the lens can be masked to block
the view of undesired areas (refer to section I. Lens Masking).
• The Sensor’s detection range is dependent on the ceiling height, as shown in the
table below.
Temporary Mounting Methods
If you are uncertain about correctly positioning the Sensor, the following temporary
mounting and testing procedures are recommended to verify proper performance
before permanently installing the Sensor.
Temporary Mounting: Drop Ceiling
Use this procedure if the Sensor will be mounted on a ceiling tile.
The ceiling tile mounting wire is provided for both temporary and permanent mounting
of the Sensor to drop ceilings composed of multiple tiles. It is designed to allow
temporary mounting, testing, and repositioning (if necessary) of the Sensor without
damaging a ceiling tile. Once the Sensor’s fi nal position has been chosen, the
mounting wire can be twisted to lock the Sensor in place permanently.
Insert the ceiling tile mounting wire
through the two smaller holes in the
mounting bracket and replace the
mounting bracket.
Temporarily mount Sensor to a ceiling tile by
inserting the wire legs through the tile, making
sure the Sensor is fl ush to the tile.
1.1
1.2
Note: Do not twist wire legs together until
G. Permanent Mounting Methods.
1.2
2.2
Hallway falls
within Sensor’s
coverage
area.
Lens sections
shown in white
are masked
with labels Lens Mask
Lens sections
shown in gray have
not been masked
2.1
2.4
2.3
G
I
Permanent Mounting Methods
Permanent Mounting: Drop Ceiling
After the Sensor has been temporarily mounted, leave the Sensor in place on the
tile and either take the tile down or remove an adjacent tile to gain access to the
legs of the mounting wire on the back of the tile.
Twist the wire legs together
tightly so the mounting bracket
remains snug against the tile.
Then replace the tile.
Permanent Mounting: Solid Ceiling
Drill two 3/16 in (4.6 mm) pilot holes for the provided screw anchors.
Press the anchors into the holes and tap fl ush with a hammer.
Place the fl at side of the mounting bracket against the
ceiling and install the two provided screws using a hand
screwdriver.
Attach the Sensor to the mounting bracket by
inserting and twisting in a clockwise direction
until the Sensor locks into place.
1.1
1
2
1
ETesting Sensor Coverage
With the Sensor mounted on the ceiling, press and
release the “Test: Sensor” button on the front of the
device. The lens will glow briefl y, indicating the test
mode has been entered.
NOTE: There is a warm-up period of approximately
90 seconds after the batteries are installed before the
test mode can be activated. If the button is pressed
during this time, the lens will fl ash continuously until
the warm-up period is complete, and then the test
mode will be automatically entered.
Timeout
30 min
15 min
5 min
Auto-On Activity
Always
Low light
Disable
HAdvanced Set-Up (Optional)
The Sensor features several advanced set-up modes. For the majority of installations,
the default settings will provide the best performance and you will not need to utilize
the advanced set-up.
The Occupancy version of the Sensor has three adjustable advanced set-up modes:
Timeout, Auto-On, and Activity. The Vacancy-Only version has only two modes
(Auto-On not available). The default settings are listed below.
Default Settings:
Timeout: 15 minutes
Auto-On: Always (Occupancy version only)
Activity: Low Activity
Advanced Set-Up Modes
Timeout
The Sensor will turn the lights off if no motion occurs for the duration of the timeout
period. There are four available timeout settings: 1, 5, 15, and 30 minutes.
Auto-On (Occupancy version only)
The automatic-on functionality of the Sensor can be adjusted to control how the
lights respond upon initial occupancy. There are three available settings: Always, Low
light,
and Disable.
Always: The lights will always turn on.
Low light: The lights will only turn on automatically upon entry if there is not already
suffi cient ambient light in the room.
Disable: This setting converts the Sensor to vacancy mode. The lights will not
automatically turn on but will still automatically turn off after vacancy. The lights must
be manually turned on by using the associated dimming or switching device.
NOTE: The 15-second vacancy grace period is active in this mode. Refer to the
Sensor Operation section at the beginning of this document for more details.
2
3
4
5
1
2
3
F
Confi rm the coverage area by walking through the space and observing the lens.
The lens will glow solid every time motion is detected. If the lens remains off during
motion, the Sensor cannot detect motion at that location.
Press and release the “Test: Sensor” button again to exit the test mode. If the button
is not pressed, the test mode will automatically time out 15 minutes after being
enabled, or 5 minutes after the last detected motion if the room is vacated.
If the Sensor has signifi cant trouble detecting motion during the test, it should be
moved to another location and retested. If the Sensor still has poor detection from
the new location, refer to the Troubleshooting section.
NOTE: If the Sensor is detecting motion in areas that are not desirable, such as
hallways or adjacent rooms, refer to section I. Lens Masking.
If Sensor detection is satisfactory during this test, perform the wireless
communication test as described in section F. Testing Wireless
Communication.
Testing Wireless Communication
This test should be performed to verify that the Sensor has been correctly set up
with the corresponding dimming or switching device and that there is proper
wireless communication from the chosen Sensor location.
If the lights in the room are not on, turn them ON manually at the dimming or
switching device.
Press and release the “Lights Off”
button on the front of the Sensor. The
lights should turn OFF.
Press and release the “Lights On”
button on the front of the Sensor. The
lights should turn ON.
If the lights do not respond correctly,
refer to the Troubleshooting section.
Symptom Possible Causes Solution
Lights do not turn ON when space is
occupied.
Sensor is not correctly added to dimming / switching device(s). Refer to section B. Set-Up.
Sensor’s Auto-On setting is set to “Low light” or “Disable”. Refer to section H. Advanced Set-Up.
The lights were recently turned off manually and the timeout has
not yet expired.
For more details, refer to Frequently Asked Questions at www.lutron.com/occsensors
Sensor does not have full view of room. Refer to section C. Sensor Placement and Coverage.
Sensor is outside wireless range of dimming/switching device. Refer to section C. Sensor Placement and Coverage or F. Testing Wireless Communication.
Battery has been installed incorrectly. Refer to section A. Pre-Installation.
Dimming/switching device has been improperly wired. Refer to the instruction sheet of the receiving device or call Lutron Technical Support Center at 800.523.9466.
Light bulb(s) burned out.
Breaker is off or tripped.
Lights turn OFF while space is occupied. Sensor’s timeout is too short for this application. Refer to section H. Advanced Set-Up.
Sensor does not have full view of room. Refer to section C. Sensor Placement and Coverage.
Lens mask is improperly applied. Refer to section I. Lens Masking.
Sensor’s activity setting is too low. Refer to section H. Advanced Set-Up.
Lights stay ON after space is vacated. Sensor’s timeout has not yet expired. Refer to section H. Advanced Set-Up.
An external noise source such as an HVAC vent is interfering. Try moving Sensor to a new location or reducing sensitivity. Refer to section C. Sensor Placement and
Coverage or H. Advanced Set-Up.
Battery has been installed incorrectly. Refer to section A. Pre-Installation.
Lights turn ON when walking past room. Sensor coverage extends beyond room perimeter. Refer to section C. Sensor Placement and Coverage or I. Lens Masking.
Behavior of lights does not match Sensor
settings.
The intended setting was not saved. Refer to section H. Advanced Set-Up.
Multiple Sensors are added to a dimming/switching device and
their settings do not match.
Refer to section H. Advanced Set-Up.
Sensor lens does not glow in response to
motion during Sensor coverage testing.
Sensor cannot see motion due to obstruction. Move Sensor to another location. Refer to section C. Sensor Placement and Coverage.
Room is too big or oddly shaped. Multiple Sensors may be necessary for full room coverage. For more details, refer to Frequently Asked
Questions at www.lutron.com/occsensors
Battery has been installed incorrectly. Refer to section A. Pre-Installation.
Lens does not stop glowing during Sensor
coverage testing even when there is no
motion.
An external noise source such as an HVAC vent is interfering. Try moving Sensor to a new location or reducing sensitivity. Refer to section C. Sensor Placement and
Coverage or H. Advanced Set-Up.
Lights do not respond correctly during
wireless communication testing.
Sensor is not correctly added to dimming / switching device. Refer to section B. Set-Up.
Sensor is outside wireless range of dimming/switching device. Move Sensor closer to dimming/switching device and retry test. Refer to section F. Testing Wireless
Communication.
Battery has been installed incorrectly. Refer to section A. Pre-Installation.
Dimming/switching device has been improperly wired. Refer to the instruction sheet of the receiving device or call Lutron Technical Support Center at 800.523.9466.
Light bulb(s) burned out.
Breaker is off or tripped.
Sensor lens fl ashes and lights do not turn
ON when space is occupied.
Battery is low. Replace battery. For more details, refer to Frequently Asked Questions at www.lutron.com/occsensors
Sensor is in test mode. Remove sensor from test mode. Refer to section E. Testing Sensor Coverage.
Troubleshooting
Battery
Release
Tab
FCC Information
NOTE: This equipment has been tested and found to comply with the limits for a Class B digital device,
pursuant to part 15 of the FCC rules. These limits are designed to provide reasonable protection against
harmful interference in a residential installation. This equipment generates, uses and can radiate radio
frequency energy and, if not installed and used in accordance with the instructions, may cause harmful
interference to radio and television reception, which can be determined by turning the equipment off and
on. The user is encouraged to try to correct the interference by one or more of the following measures:
· Reorient or relocate the receiving antenna.
· Increase the separation between the equipment and receiver.
· Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
· Consult the dealer or an experienced radio/TV technician for help.
Caution: Changes or modifi cations not expressly approved by Lutron Electronics Co. could void the
user’s authority to operate this equipment.
This device complies with Part 15 of the FCC rules. Operation is subject to the following two conditions:
1. This device may not cause harmful interference, and
2. This device must accept any interference received, including interference that may cause undesired operation.
1.3
1.4
1.5
Perform the Sensor coverage and wireless communication tests as described in sections
E. Testing Sensor Coverage and F. Testing Wireless Communication.
If the Sensor does not perform satisfactorily from this location, it may be moved to another
location by pulling the Sensor straight down and repeating steps 1.2 and 1.3.
If the Sensor’s performance is satisfactory, it should be permanently attached to the
ceiling tile, as described in section G. Permanent Mounting Methods.
1.1
1.2
1.3
1
2.1
2
2.2
Dimmer Switch
NOTE: Do not over-tighten.
Coverage Chart (for sensor mounted in center of room)
Ceiling
Height
Max. Room Dimensions
for Complete Coverage
Radius of Coverage
at Floor
8 ft (2.4 m) 18 x 18 ft (5.5 x 5.5 m) 13 ft (4.0 m)
9 ft (2.7 m) 20 x 20 ft (6.1 x 6.1 m) 14.5 ft (4.4 m)
10 ft (3.0 m) 22 x 22 ft (6.7 x 6.7 m) 16 ft (4.9 m)
12 ft (3.7 m) 26 x 26 ft (7.9 x 7.9 m) 19 ft (5.8 m)
Activity
The sensitivity of the Sensor can be adjusted based on the expected level of activity within
the room. There are three available activity settings: Low Activity, Medium Activity, and
High Activity.
Low Activity: This is the most sensitive setting and will detect very slight motions. This is
the recommended setting, as it will work well for nearly all applications. It is ideal for spaces
where occupants will often be seated for long periods of time.
Medium Activity*: This setting is slightly less sensitive than the Low Activity setting and
can be used for spaces that experience normal activity.
High Activity*: This is the least sensitive setting and can be used for spaces that will
generally only experience large motions, such as foot traffi c.
* The Low Activity setting is the default and will perform best for most applications. Rarely, if the Sensor is
placed near external noise sources such as heating vents, air conditioning vents, or light bulbs, it may turn
the lights on without occupancy or keep the lights on too long after vacancy. If this occurs, changing the
sensitivity to Medium Activity or High Activity should resolve the problem.
Advanced Set-Up Operation
The advanced set-up is accessed by using the buttons on the back of the Sensor.
Check Settings
To display the current setting, press and release the desired button. An LED will
illuminate briefl y, indicating the current setting.
Change Settings
The standard settings for Timeout, Auto-On, and Activity are changed using the
procedure described below in the left column. The procedure for selecting a
1-minute timeout is slightly different and described below in the right column.
Standard Modes 1-Minute Timeout*
1To adjust a setting, press and
hold the desired button until the
LED corresponding to the current
setting begins fl ashing rapidly,
indicating the setting can now be
adjusted.
1To select a 1-minute timeout, press
and hold the timeout button for
approximately 10 seconds until all 3
LEDs begin fl ashing rapidly.
2Each subsequent button press of
less than 2 seconds will increment
to the next available setting.
Pressing any of the other buttons
will have no effect.
2To save the 1-minute timeout setting,
press and hold the timeout button until
all 3 LEDs turn on solid, indicating the
1-minute timeout has been saved.
3To save the selected setting, press
and hold the button until the LED
turns on solid. This indicates the
saved setting.
* The 1-minute timeout is intended for use in high-
activity, briefl y occupied areas only (e.g., closet,
laundry room, etc.). Do not use this setting in areas
that experience minor motion or extended occupancy
(e.g., offi ce, bathroom, etc.), as the lights may
unexpectedly turn off.
Lens Masking (Optional)
Whenever possible, the Sensor should be installed in a location where it cannot easily see
into areas outside the intended space, such as hallways or adjacent rooms. If this situation
cannot be avoided, portions of the lens may be masked with the provided labels to block
the Sensor’s view of the undesired areas.
Note: Apply mask to outside of lens only; do not disassemble sensor.
· It is recommended to remove the Sensor from the mounting bracket before applying the
masking labels.
NOTE: The Sensor can be screwed onto the mounting bracket in several
different orientations. Be sure to note the Sensor’s orientation before taking it down and
replace the Sensor in the same orientation to ensure the intended area gets blocked.
· Outer lens sections correspond to the detection regions furthest away from the Sensor,
while inner sections correspond to regions closer to the Sensor.
· Be careful when applying the labels to avoid creating gaps between adjacent masked
sections. The Sensor may detect motion through inadvertent gaps.
3
3.2

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