from
The Free On-line Dictionary of Computing (8 July 2008)
channel service unit
<communications> (CSU) A type of {interface} used to connect a
{terminal} or computer to a digital medium in the same way
that a {modem} is used for connection to an analogue medium.
A CSU is provided by the {communication carrier} to customers
who wish to use their own equipment to retime and regenerate
the incoming signals. The customer must supply all of the
transmit logic, receive logic and timing recovery in order to
use the CSU, whereas a {digital service unit} DSU performs
these functions.
(1995-01-30)