An engagement wheel is mounted so that it can rotate relative to the drive shaft of a drive train in a motor vehicle. The surface treatment involves contacting at least one porous surface of the film with plasma at atmospheric pressure and a plasma generating electrode frequency of greater than 1 MHz. Said second phase error detecting means receives said robust phase error signal and generates therefrom a frequency sensitive phase error signal which is representative for the frequency error or frequency offset between the frequency of the receiver and the frequency of the carrier of the received digital input signal.