Abstract: In a sound system having a sound source for generating sound signals, a low-impedance amplifier for amplifying the generated sound signals, and high-impedance loudspeakers for reproducing audible sound from the amplified sound signals, an impedance conversion device having a step-up transformer section is disconnectably connected between the amplifier and the high-impedance speakers. The output side of the low-impedance amplifier is also connected directly to low-impedance loudspeakers. Thus the sound system can be operated to selectively broadcast either monaural sound or binaural stereo music of high quality.

Abstract: A guidance apparatus in case of emergency evacuation comprising a laser which is disposed within a building or the like in such way that a laser beam emitted from the laser is directed in the direction in which evacuees must escape or is directed from the side of an emergency exit toward the interior of the building or the like; abnormal condition detection means for detecting the occurrence of an abnormal condition in the building or the like and generating a detection signal representative of the occurrence of an abnormal condition; and a control unit which is connected to the laser and the abnormal condition detection means and which, in response to the detection signal, energizes the laser. When an abnormal condition such as fire occurs within the building or the like, the detection means detects the occurrence of an abnormal condition and generates a detection signal, in response to which the laser in energized to emit a laser beam directing the direction in which evacuees must escape.

Abstract: A flat speaker device having a flat speaker unit fitted into a through-hole for mounting a speaker of a wall surface board having its back secured to a wall surface leaving a specific spacing therebetween, the flat speaker unit comprising a total-drive type flat speaker comprising a plurality of magnets juxtaposed on a plane and a diaphragm formed from a plurality of projections for respectively covering the plurality of magnets, a speaker frame with a mounting flange mounted on the flat speaker so as to encircle the outer periphery of the flat speaker, rod-like screw members mounted so as to pass through the speaker frame from the front surface towards the back, and swining blades each disposed on the back of the speaker frame with one end threadedly engaged with a respective rod-like screw member and having a length such that when the blade is swung outwardly of a diagonal line of the speaker frame, the tip portion of the blade extends outwardly from the speaker frame.