Installation Manual

EXI HALO Installation Manual Rev 2.0
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EXI Wireless Systems Inc. Page 8 June, 1999
- The field should not extend into other rooms or areas that are regularly occupied
by tags. These tags could keep a controller in a pre-alarm state preventing the
door from opening if magnetic door locks are being used.
- The tag should also be detected at least 4 feet from the door in order to give the
magnetic door lock time to energize.
- Proximity to other fields could also be a factor. If a Tag is able to receive com-
munication from 2 different controllers in the case of field overlap, it will try to
respond to both controllers. Each controller will see Tag communication when it
doesn’t expect it and report it as noise.
Ceiling height, door approach width and metal in the vicinity, need to be considered when planning the
location for the exciter antennae. The field should extend to the floor and from wall to wall. A dropped
ceiling consisting of a grid and non-foil backed ceiling tile are the easiest construction materials to
work with. Check above the lay-in tile to see how much space you have and the proximity of metal ob-
jects such as pipes, cables and air plenums. The SRA may also be dropped inside a wall cavity. Some-
times it’s simpler to mount the SRA on the side of a wall above the door or along the hallway about 5
feet from the floor.
Extensive metal close to the Exciter can distort the field in unpredictable ways. Metallic objects will
absorb and/or reflect radiated energy, which affects the field. This phenomenon can increase or decrease
the field strength in areas causing hot spots or holes in your field. It can even change the shape of the
field with tag detection sometimes occurring as much as 35 ft away. At times this effect can be used to
advantage but the desired result can only be determined experimentally.
Although it is not possible to completely predict the performance of the field for every situation, some
information about the field will help to shorten the process of determining the best location for the
SRA. In the absence of any site irregularities, the field is symmetrical perpendicular to the antenna
length. A cross-section through the length of the antenna is roughly oval as shown below.
Figure 5 – Antenna Field
Although the field strength is adjustable, the maximum distance for good coverage is approximately 10
feet. Sometimes 2 exciters are necessary to get adequate coverage.
The location of the SRA is limited only by your imagination. If you have a location where you would
like to mount it, try it. If it doesn’t work, try something else. The important thing is that it must work
well in its location. Each field needs to be fully tested to ensure adequate coverage of the protected
If it’s not possible to create a proper field with the exciter
inside, an SRA-E exciter antennae for outdoors could be
placed on an outside wall to limit the penetration of the
field into the building.