With reference to both analog and digital interfaces, the ATM functional unit and technology that operates with analog 2-wire interfaces and standard digital line rates on both the inputs and the outputs, e. G. , DS1 on the input and DS3 on the output, and which passes the cells received on the input to the output. The relationship between input and output, can change on a per call basis, i.e., switched virtual circuits must be supported and permanent virtual circuits may be supported. (For the purposes of this document it is assumed that the cell formation function associated with an analog input is performed before the switch function occurs. However, this definition is not intended to constrain technical implementations. ) This device allows blocking and concentration. The switch function is also required to perform 2-wire to 4-wire conversion as well as A/D conversion. 2. With reference to digital interfaces only, the ATM functional unit and technology that operates with cell-based signals and over standard line rates on both the inputs and the outputs, e. G. , DS1 on the input and DS3 on the output, and which passes the cells received on the input to the output. The relationship between input and output, can change on a per-call basis, i.e., switched virtual circuits must be supported and permanent virtual circuits may be supported. This device allows blocking and performs concentration.