A demonstration model assembly having an anatomical model structure that is stabilized by a support in a relatively compact area on a stable surface is provided. The changeover switch includes a default state of connecting the rechargeable battery to the comparator, so that the comparator produces a comparison result by comparing a battery voltage of the rechargeable battery with a preset voltage threshold. In one embodiment, the capacitive coupling per unit length between the first line and the second line is approximately equal to k and the impedance of the first pair of impedance elements is approximately equal to 1, where is the speed of light through a dielectric in which the first and second lines are located. The first and second profiles are releasably engageable to each other. The interactive station controller receives the message signal and generates from it a viewer message.