6-amino–7-methyl-1H-benzimidazole-4-carbonitrile substantially free of 2,3,7-triamino-4,6-dimethyl-1,9-phenazinedicarbonitrile, and the anhydrous monoacetate salt thereof, are useful in the treatment of alpha-2 mediated disorders such as ocular hypertension. In one embodiment, a first optical amplifier Raman amplifies a wavelength division multiplexed signal light in both a first wavelength band and a second wavelength band in accordance with a plurality of excitation lights provided to the first optical amplifier, the first and second wavelength bands being different from each other. When the signal is not passed, the respective four field effect transistors are put in operation, thereby eliminating the effects of standing waves occurring on the respective paths leading to the four signal terminals acting as open ends. The composition is suitable for producing a variety of molded article most notably optical data storage media. A target ventilation is taken as 95% of the longterm average ventilation. The output from the counter is bit-by-bit ANDed with the output of the register, and those outputs are XORed together to output a single bit.