The DataSMART 658 Single-Port Add/Drop DSU/CSU is designed for businesses that require both voice and data services. With the DataSMART 658, you can integrate your voice traffic from a T1 PBX and data or Internet traffic onto a single T1/FT1 line, avoiding multiple WAN access charges.??The DataSMART 658 key features are: economical integration of data and voice traffic, Add/Drop port is compatible with T1 multiplexers, compatibility with all routers, and PBXs with T1 interface, simplified local management via Ethernet connection and front-panel LCD.