A system and method are provided for selecting an optimal threshold detection level for a single serial data input receiver. The method comprises: receiving a serial data stream of pseudorandom binary information; using a plurality of threshold detection levels, estimating bit values; comparing the differences between estimated bit values; and, adjusting the threshold levels to minimize the difference between comparisons of estimated bit values. In some aspects, comparing the differences between estimated bit values includes: counting a first number of differences between the first and third thresholds; counting a second number of differences between the second and third thresholds; and, adjusting the first and second thresholds until the first number equals the second number.