BMW 2001 325CI, Manual

Page: 190 / 215

190 n
Radio reception Safety belt tensioner
The AM frequency bands (medium-
wave, long-wave and short-wave) make
it possible to receive stations from a
great distance, because the broadcast
signals travel not only along the ground
as surface waves, but also as atmo-
spheric waves that are reflected from
the ionosphere.
Frequency modulation (FM) offers
substantially better sound quality than
the other frequencies. However,
because FM transmissions rely on line-
of-sight broadcast waves, their effec-
tive reception range is limited.
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The limitations inherent to radio recep-
tion in a moving vehicle have been
minimized by a number of innovative
system designs:
The "Radio Data System" (RDS) makes
sure that, for broadcast stations
sending on several frequencies, the
radio automatically tunes to the
frequency with the best reception
quality.
The Antenna Diversity system employs
several FM antennas integrated within
the rear window to provide three sepa-
rate sources for receiving broadcast
waves. An integral processor automati-
cally selects the antenna with the best
FM reception quality at any given time.
The selection of the antenna takes
place within milliseconds, and is
therefore not noticed by the radio
listener.
The safety belt tensioner makes sure
that the belt tightens during a head-on
collision to ensure that occupants
remain firmly positioned in their seats.
A gas-pressure system retracts the
buckle assembly to tension the
shoulder and lap belts within fractions
of a second. This reduces the tendency
to slide under the lap belt.
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