This Cisco network interface card will provide the most reliable network connections and expand network capabilities of your Cisco router.The 4-wire 56k CSU/DSU implements switched 56k and DDS (leased line) operation. The hardware feature set is identical to the 4-wire 56/64k CSU/DSU for the Cisco 2524 and Cisco 2525; the Cisco IOS configuration is also the same.