Abstract: Disclosed is a duplex system having a function to suppress radio wave radiation. To suppress unnecessary radiation of radio waves from duplex clock signal lines, the system comprises a plurality of cards each for mounting electronic devices, a backboard for supporting the plurality of cards to be standing closely together in parallel, a first and a second clock signal sources for respectively generating a first and a second clock signals, a first and a second selecting gates for alternatively selecting one of the first and second clock signals to be output, and a first and a second group of clock signal lines, the clock signal lines in the first and second group respectively being wired closely in parallel on the backboard and wired on the cards, for respectively conducting the first and second clock signals to the cards.

Abstract: A synthetic resin lens having a refractive index of at least 1.55 and an antireflection coating thereon is provided. The antireflection coating includes at least a hard coat layer formed of a dielectric substance having a refractive index n.sub.h disposed on the lens having a refractive index n.sub.s (n.sub.s .noteq.n.sub.h) and at least one antireflection layer of a dielectric or metallic material disposed between the lens and the hard coat layer. The antireflection layer has a refractive index n in the range represented by the formula: ##EQU1## and an optical film thickness of 4 (where denotes a wavelength in the range between about 450 nm to 650 nm) or two or more plies optically equivalent to a single layer of the antireflection material. The synthetic resin lens may be prepared by radical polmerization of a mixed monomer solution of styrene, 2,2-bis[3,5-dibromo-4-(2-methacryloloxyethoxy)phenyl]propane, and ultraviolet absorber and a light stabilizer.