CSU (channel service unit)
A device found on digital links that transfers data faster than a modem (in a range from 56 kilobits per second to 1.5 megabits per second) but does not permit dial-up functions. It also performs certain line-conditioning and equalization functions, and responds to loop-back commands sent from a central office. A CSU is the link between digital lines from the central office and devices such as channel banks or data communications devices.
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