Mercedes-Benz 2005 C 240 Operator's Manual page 214

Controls in detail
Audio system
Switching between calls
Press s button.
This switches between the calls.
The non-active call is kept on hold.
Terminating a call
Press t button.
The current call is terminated. The
connection to the caller previously
kept on hold is also interrupted;
however, reconnection is indicated
by an acoustic signal.
212
Placing a second call
If you wish to place another call during an
already active call, you can place the
second call and switch between the callers
or combine them into one call. Note that
this feature is depending on availability
from your mobile phone service provider.
Placing a second call
Place a new call by entering
telephone number manually.
Press s button.
You are connected to the second
caller; the first caller is kept on
hold.
Terminating a call
Press t button.
The current call is terminated. The
connection to the caller previously
kept on hold is also interrupted;
however, reconnection is indicated
by an acoustic signal.
Combining two calls
Press s button.
The calls are combined into one
call.
Terminating a combined call
Press t button.
The connection to both callers is
terminated.