E85 Information/Communication
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- Transmission
The system uses the licence-free, global industrial scientific
medical band (ISM) at 2.45 GHz. This frequency range from
2.402 GHz to 2.480 GHz is subdivided into 79 channels at
1 MHz bandwidth.
The channels are changed 1600 times per second to avoid inter-
ference in connection with other devices and to make inter-
ception more difficult.
Fig. 51: Frequency change during data transfer
Note:
The signal range is shortened substantially when using the
hands-free facility to make a call together with the Bluetooth
mobile phone and turning the head into the transmitter range
from the Bluetooth mobile phone to the Bluetooth aerial.
The attenuation is particularly high when an obstruction
contains water molecules.
Reason:
The resonance frequency of water approximately corresponds to
the transmit frequency of the ISM band.
KT-10769
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