Although the design of medical ultrasonic diagnostic equipment of the pulse-echo type is solidly based on industrial flaw-detection technology, it must also be influenced by a number of considerations peculiar to electro-medical equipment. For example, there is a requirement for a margin of safety from electrical or other injury somewhat greater than that normally regarded as adequate commercially. Simplicity of control and presentation is at a premium and regard must be paid to the preservation of the confidence, comfort and dignity of a patient. Perhaps to a greater degree than in industrial flaw-detection, a significant measure of operator skill and dexterity is involved in obtaining an adequate result, and in medicine the initiative in devising new techniques lies much more with the user than in industry.