Which of the following is a hardware device that converts a digital data frame from the communications technology used on a local area network (LAN) into a frame appropriate to a wide-area network (WAN) and vice versa?

CSU/DSU (Channel Service Unit/Data Service Unit)

Explanation:

A CSU/DSU (Channel Service Unit/Data Service Unit) is a electronic interface that connects data terminal hardware, such as a modem, a digital circuit.

The CSU / DSU has two distinct tasks to implement.

The channel service unit (CSU) is accountable for the telecommunications network connection, whereas the data service unit (DSU) is accountable for the management of the DTE interface.