In
telecommunication, a
channel service unit (CSU) is a
line bridging device that (a) is used to perform
loop-back testing, (b) may perform
bit stuffing, (c) may also provide a
framing and formatting pattern compatible with the
network, and (d) is the last
signal regeneration[?] point, on the loop side, coming from the
central office, before the regenerated signal reaches a
multiplexer or
data terminal equipment (
DTE).
Source: from Federal Standard 1037C
See also: CSU/DSU[?]