Apparatus for testing the performance of a communication line that carries customer data between two modems, including a programmable processor (for example, a digital signal processor) in each modem that either performs modulation or demodulation of customer data or tests the line, and a controller...http://www.google.ca/patents/US4918623?utm_source=gb-gplus-sharePatent US4918623 - Testing the performance of a communication line between two modems using modem processor
