An ultrasound diagnostic apparatus is provided. According to the invention, the digital data to be transmitted according to a data transmission protocol is divided into individual data packets in each of two transmittingreceiving stations. Torsion springs are mounted between the housing and the intumescent material to surround the conduit and are held in a non-operational position by fusible links. At least one heat-absorbing material is positioned within the bit body at least proximate to the at least one cutting element. The power supply wires 20 having high tensile strength enables to suspend the electrical apparatus and also supply power thereto. A third overlay can be attached to and extend across the top of the door, perpendicular to the overlays which extend along the sides of the door to cover the space between the top of the frame and the top of the door.