B-SCAN PRESENTATION:-The B-scan presentation is a profile (cross - sectional) view of the test specimen. In the B - scan, the time - of - flight (travel time) of the sound energy is displayed along the vertical axis and the linear position of the transducer is displayed along the horizontal axis. From the B - scan, the depth of the reflector and it's approximate linear dimensions in the scan direction can be determined. The B - scan is typically produced by establishing a trigger gate on the A - scan. Whenever the signal intensity is great enough to trigger the gate, a point is produced on the B-scan. The gate is triggered by the sound reflecting from the Blackwall of the specimen and by smaller reflectors with in the material. In the B-scan image above, line A is produced as the transducer is scanned over the reduced thickness portion of the specimen. When the transducer moves to the right of this section, the Blackwall line BW is produced. When the transducer is over flaws B and C, lines that are similar to the length of the flaws and at similar depths within the material are drawn on the B - scan. It should be noted that a limitation to this display technique is that reflectors may be masked by larger reflectors near the surface.