Abstract: An ultrasonic system for determination of bone characteristics is provided having first and second transducers in a mounting arrangement for mounting the transducers in spaced relationship with respect to the bone, the mounting arrangement including a contact arrangement for defining a stable and repeatable contact point on the body part containing the bone, such that the transducers may be biased against the body part with a substantially constant force, the contact arrangement including a plurality of contact buttons projecting in a common direction, the buttons being axially displaceable and fitted with an engagement sensing arrangement for determining contact with the body part such that operation of the device may be inhibited until proper contact is made.