In the broadband network access device for transmitting narrowband, low-frequency voice signals and broadband, higher-frequency data signals, the voice data is sampled in the data clock pattern and subsequently decimated. The transmission of the data which has already been decimated to the voice clock to the voice DSP (DSP) is still carried out in the data clock pattern. The conversion to the voice clock pattern is carried out in a synchronization interface (SM), directly upstream of the voice DSP. The same applies correspondingly in the opposite direction of transmission. The invention is used in xDSL methods, for example ADSL.Lite.