loopback test A test of a local loop initiated by a local exchange carrier (LEC) at the network edge and causing a contact closure at the network interface unit (NIU) on the customer premises. The loopback test thereby allows the testing of the local loop in the forward direction, through the NIU, and loop-ing in the backward direction, all in isolation from the customer premises equipment (CPE) and wiring. See also CPE, LEC, local loop, and NIU. |