A pulse response for a receiver, as an array PR, is found from the receiver's symbol stream. For a continuous stream of arbitrary data, a value of the array PR[k] can be determined from the signal levels of the symbols received. The stream of received data is input to a FIFO. Between the first and last locations of the FIFO is the symbol referred to herein as Dn. Symbols located in the FIFO before Dn are referred to as Dn−x. Symbols located in the FIFO after Dn are referred to as Dn+x. Dn differs from the other FIFO symbols in that its signal level can be measured with an adjustable error slicer. The ISI effect of any Dn−k upon Dn can be measured, and thus any PR[k] measured, by measuring the average signal level of Dn when only certain types of data streams occur in the FIFO.