ADSL System reference model, which is shown in
figure 
, describes the basic blocks of an
ADSL-system.
The decomposed and routed data from the access module, see
figure , is connected to an ATU-C (ADSL Transceiver
Unit - Central Office) in which the data will be converted into analog
signals. The analog signals are then carried with POTS signals to
remote end. ATU-C also receives and decodes data coming from customers
premises send by ATU-R (remote).
Both ATU-C and ATU-R (ADSL Transceiver Unit) are described in more
detail in figures and .
The splitter either combines or separates the signals depending on the direction of the transmission. It protects MTS from voice-band interference generated by both ATU's and on the other hand it protects ATU's from MTS-related signals.
Figure: ADSL System Reference Model
Figure: ATU-C Transmitter reference model
Figure: ATU-R Transmitter reference model