Patent ID: 7383518

Claim:
A method for determining a non-normal differential signal level (NNL) that is associated with a non-normal symbol error rate (SER) for a data transmission system, the method comprising: receiving the non-normal SER for the data transmission system, wherein the non-normal SER is greater than the data transmission system's SER under normal operating conditions; receiving an input differential signal at an input of an adjustable DC-offset-circuit, wherein the input differential signal is received through coupling capacitors which are coupled with a transmitter, wherein the adjustable DC-offset-circuit generates an output differential signal on an output of the adjustable DC-offset-circuit, wherein the output of the adjustable DC-offset-circuit is coupled with an input of a receiver, and wherein the adjustable DC-offset-circuit is used to determine the NNL; determining an initial value for the NNL; determining a final value for the NNL level by: using the receiver to measure a first SER; comparing the first SER with the non-normal SER; and adjusting the output differential signal of the adjustable DC-offset-circuit in response to determining that the first SER is not substantially equal to the non-normal SER; and recording the final value for the NNL, which is subsequently used to estimate the data transmission system's SER under normal operating conditions.