A cable channel filler or spline and a cable containing the cable channel filler or spline in its core. The mating flap roll, which bears the suction element that turns the mating flaps over, has a radius that is reduced on a part of the roll’s circumference that is not equipped with the suction element. The devices along the route now communicate with only one vehicle of the virtually coupled trains. A synthesizer may synthesize part of the first microphone signal by processing the second microphone signal.