A display includes a plurality of display areas connected with each other, each operable to variably and stationarily display one kind of plural hexagonal indicium. The apparatus has a pressing device, a conveyor belt, and a further device for covering the substrate with a protective film. This configuration permits the amplifier circuit to operate as a linearized Class C amplifier, having a substantially linear input-output relationship similar to that of a Class B amplifier, but with increased operating efficiency.