Abstract: Systems and methods are disclosed for determining characteristics of a communications medium, such as a subscriber loop. In one embodiment, a system is disclosed to determine at least one characteristic associated with a subscriber loop. The system includes memory that stores data indicative of signal responses and loop characteristics for a plurality of loop configurations. A processor is programmed to ascertain at least one loop characteristic associated with the subscriber loop based on evaluation of data associated with a signal response received via the subscriber loop relative to at least a portion of the data indicative of signal responses stored in the memory.

Abstract: System and method for a multi-standard sigma-delta modulator. A preferred embodiment comprises an integrator coupled to a signal input, wherein the integrator is configured to sum a difference between an input signal and an output of the sigma-delta modulator. A dithering circuit, also coupled to the signal input, is used to produce a dithering sequence. A summing point combines an output of the integrator and the dithering circuit while a quantizer converts the combined outputs into one of several discrete levels. The sigma-delta modulator further comprises a reset circuit to reset the sigma-delta modulator if the integrator becomes saturated. The sigma-delta modulator, as described, is compatible with G.Lite, ADSL, and ADSL+ variants of the digital subscriber line technical standards.