Main Page | See live article | Alphabetical index In telecommunication, a customer service unit (CSU) is a device that provides an accessing arrangement at a user location to either switched or point-to-point, data-conditioned circuits at a specifically established data signaling rate. Note: A CSU provides local loop equalization, transient protection, isolation, and central office loop-back testing capability. Source: from Federal Standard 1037C This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.