A method and apparatus for measuring the quality of live, standing timber employs deep-set spike probes angled to create a longitudinal compression wave. Since the projector includes a communication unit configured to receive an electronic mail, the projector updates an image signal and adjusts a diffusion degree of modulated light by a light-diffusion adjusting unit on the basis of contents of the mail received by the communication unit. It takes advantage of modern micro controller technology with integrated memory, digital inputoutput, sensor and timer channels to produce a low parts count, as well as reliable operation in a large variety of vehicles, even when installed by people with little experience or knowledge in this area. The information is provided to the user in such a manner that the user can perceive the execution results easily. Each of the heating pads of the sauna apparatus includes a flat heating body, and a flat electrical insulator enclosing the flat heating body. The bias is strong enough to provide the fluid seal so that the seal is not compromised when the pressure difference between the inlet and the outlet is small.