Cisco SPA-4XT-SERIAL : Cisco 4 port serial SPA

The Cisco 4-Port Serial SPA delivers flexible, high-performance WAN connectivity for enterprise and service provider networks. It provides four synchronous serial ports, each capable of speeds up to 8 Mbps.
The Cisco 4-Port Serial SPA supports a variety of interface types determined by separately purchased cable type connected to it. The supported electrical standards include EIA-232, X.21, V.35, EIA-530, EIA-530A, and EIA-449. Each port can be configured independently of the others to provide superior flexibility. Also depending on the cable type, each interface can either be configured for Date Terminal Equipment (DTE) or Data Communications Equipment (DCE).
The serial interfaces can be used to aggregate WAN connections from remote sites. The ability to support 8 Mbps per port is ideal for low- and medium-density aggregation at the head end (Figure 2.) The Cisco 4-Port Serial SPA can also be installed wherever a service provider requires an external CSU/DSU demarcation point.