CITROEN C1 2015 Handbook page 234

Audio and Telematics
DAB / FM station tracking
Digital radio does not cover 100% of
the country.
When the digital signal is weak, the
alternative DAB frequency option,
"DAB AF", makes it possible to
continue listening to the same station,
by automatically switching to the
corresponding "FM" station (if there is
one).
Press on MENU to display the list.
Turn the knob to select "Radio" then
press to confirm.
Turn the knob to select "DAB AF",
press to activate or deactivate the
frequency.
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If "DAB AF" tracking is activated,
there is a difference of a few seconds
when the system switches to the "FM"
analogue radio station with sometimes
a variation in volume.
When the digital signal is restored, the
system automatically changes back
to "DAB".
If the "DAB" station being listened to
is not available, or if "DAB AF" is not
activated, the sound will cut out while
the digital signal is too weak.