23
For instructions describing the process of setting the base to AFH or another scanning mode, see
Appendix D:
Interference Avoidance Through Spectrum Friendly
, pg. 33.
Available settings include:
High
(
H
) - Scans the Higher frequencies.
Low
(
L
) - Scans the Lower frequencies.
All
(
A
) - All frequencies are scanned.
AFH
(
E
) - (European Mode) Advanced Frequency Hopping searches for the best frequency.
EU BASE STATION ADAPTIVE FREQUENCY HOPPING
Background
The Clear-Com DX wireless intercom systems utilize a
Frequency Hopping Spread Spectrum
(FHSS) radio in order to
provide robust communications.
This system operates in the unlicensed 2.4 GHz band. With the proliferation of other devices over the past few years in
the same 2.4 GHz band, instances where these devices and systems can interfere with each other has greatly increased.
To further complicate matters, the European Union has introduced new radio standards for equipment operating
in this band in an attempt to reduce interference between equipment from different manufacturers. This European
Telecommunications Standards Institute (ETSI) harmonized European standard is known as EN 300 238 v1.8.1.
CLEAR-COM Adaptive Frequency Hopping
In order to reduce interference with other equipment and comply with these new regulations, Clear-Com has implemented
an
Adaptive Frequency Hopping
(AFH) mode for the new DX EU base stations. The key idea behind AFH is using only
the good frequencies, or channels, unoccupied by other equipment. The system scans for other signals and avoids these
signals during operation. Since the radio environment is constantly changing, there is a continuous process of scanning
for used frequencies and updating the list of good channels.
The Clear-Com system utilizes 46 discrete frequencies, or channels, within the 2.4 GHz spectrum in order to
communicate voice and data. The process of deciding which channels should be used is a 3-stage process. The process
includes scanning for occupied channels, the broadcast of a channel exclusion list and the use of the exclusion list. The
process is completed in three steps coexisting in time.
Below is the process is shown in Time. First, the system performs a channel scan to determine occupied channels. This
list is then broadcast to the communicator. The communicators and base station will use this list during period three.
The process is continuous, and as is illustrated below, the list could be constantly changing. Depending on the radio
environment, a maximum of 46 channels, and a minimum of 15 channels may be used by the system at any time.
Time
⇒
Ch. 1
Ch. 2
Ch. 3
Ch. 4
Ch. 5
Ch. 6
Ch. 7
Ch. 8
Scan
Broadcast
Use
Scan
Broadcast
Use
Scan
Broadcast
Use
Scan
Broadcast
Use
Scan
Broadcast
Use
Scan
Broadcast
Use
Summary of Contents for HME DX410
Page 35: ...35 APPENDIX E AUDIO ROUTING DIAGRAM CH B 2WT04W CH B 4WT02W CH A 4WT02W CH A 2WT04W...
Page 36: ...36...
Page 37: ...37...
Page 38: ...38...
