A power plant that outputs energy in the form of heated, compressed gas functions as a gas compressor, a motor, or a heater. A wavelength fixed type and a wavelength tunable type optical fiber grating mirrors are connected in a serial manner to constitute a dual laser mode resonator capable of simultaneously oscillating two laser modes, which are appropriate to each wavelength. The stored u-shaped frames and the front and rear signs on the frame holder also have hingedly attached signs thereon that can move from sandwiched overlapping positions to be swung out exposing indicia on the signs. The slot can extend towards and through a sidewall of the base plate, and define an outlet at a portion running through the sidewall.