Mercedes-Benz SLR McLaren. Operator's Manual.

Controls in detail
Audio system
Accepting an incoming call in cassette,
CD or radio mode
If the telephone is activated in the background
(receiving symbol S visible on display),
the audio source is muted when a
call is received. The ringing tone is heard
and the caller’s telephone number or the
name under which this telephone number
has been saved in the telephone book appears
on the display. If the caller’s number
is not transmitted, CALL appears in the display.
Press the SND key to accept the call.
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Muting a call
It is possible to mute a call; the caller is
then no longer able to hear you.
Mute on
Press the MUT key.
Mute off
Press the MUT key.
Terminating a call
Press the END key.
The current call is terminated.
Call waiting
If you receive another call during an already
active call, you can accept the second
call and switch between the two.
Accepting a second call
Press the SND key.
You are connected with the second
caller, the first call is muted.
Switching between the calls
Press the SND key.
Terminating the second call
Press the END key.
The current call will be terminated. You
are connected with the muted call
again.