Abstract: Rail testing apparatus, particularly useful at the point of manufacture, for detecting flaws in railroad rails. A number of transducers transmit ultrasonic sound waves into a rail under test and receive the associated echo signals. The apparatus advantageously divides the rail into a plurality of measured rail segments and the amount of amplification applied to the associated echo signals may be varied over each rail segment, thus providing the ability to selectively increase or decrease the sensitivity of the testing apparatus. The amplified echo signals are selectively applied to detection apparatus with a positive and negative gating scheme to increase system accuracy and reliability.