Abstract: Subscriber line maintenance apparatus and methods are disclosed. A maintenance operation is performed on a subscriber line in a communication system by an embedded test unit. The test unit limits an effect of the maintenance operation on communication signals that are transferred on the subscriber line during the maintenance operation. In one embodiment, the communication signals are high-frequency signals, and the limiting is achieved by performing the maintenance operation through a low-pass filter, such as the low pass filter of a Plain Old Telephone Service (POTS) splitter. The test unit may be implemented as a daughter card carried by another electronic circuit card in a Digital Subscriber Line Access Multiplexer (DSLAM), for example, so that the test unit does not occupy its own card slot in an equipment shelf. One, or more than one, test unit may be provided to serve multiple equipment shelves in a distributed communication equipment architecture.

Abstract: Example embodiments are directed to a system for simulating far end crosstalk (FEXT). The system includes digital subscriber lines coupled to a FEET matrix which simulates the FEXT environment. The FEXT matrix simulates the FEXT environment using filters disposed in disturber lines. Signals output from the filters are added to a path in the victim line to create an output signal.