Abstract: There is provided a distortion canceling circuit for reducing an unbalance between a higher and a lower 3rd order distortion at frequencies of (2·f2−f1) and (2·f1−f2), respectively, the distortions being generated by an amplifier which amplifies an input signal having at least two frequency components, i.e., f1 and f2. Phase modulation control means supply a control signal, which has a difference frequency of (f2−f1), to phase modulation means, the control signal being generated based on the amplified input signal outputted from the amplifier. The phase modulation means performs phase modulation on the amplified input signal based on the supplied control signal to thereby generate a higher and a lower side-band signal having frequencies of (2·f2−f1) and (2·f1−f2), respectively, each of which has an identical amplitude and a phase difference of 180° with respect to each other.

Abstract: A distortion compensating device comprises a 3 dB coupler having four terminals. The first terminal supplies an input signal to be inputted to an amplifier or is supplied with an input signal from an amplifier. The second terminal is associated with a third-order distortion generator for generating a third-order distortion having an amplitude for canceling out a third-order distortion generated by the amplifier depending on the supplied input signal. The third terminal is associated with a phase adjuster for adjusting the phase of the input signal to set the phase difference between the input signal and the third-order distortion generated by the third-order distortion generator to a phase difference for canceling out the third-order distortion generated by the amplifier.

Abstract: A repeater which is installed as measures for silent zones, which automatically compensates for a variation in a light loss caused by a difference in length among optical cables interconnecting a master device and a plurality of slave devices which are allocated and installed in an underground shopping center or the like. The master device and the slaves devices both have current detectors for detecting current values of O/E transducers which transduce received lights to electric signals. Based on the detected current values, gain control signals are applied to variable gain amplifiers to change their amplification factors so that the levels of output RF signals for transmission to a radio base station and a portable station have a prescribed value, thereby compensating for the variation in the light loss of the optical cables. The present invention greatly facilitates the installation of the repeater and additional installation of slave devices.

Abstract: A plastic lens of a stepped segment having an excellent surface hardness can be obtained at high molding efficiency from cast polymerization of a diethylene glycol bisallyl carbonate and specified acrylate(s) system further added with a specified diacrylate(s) and/or dimethacrylate(s).

Abstract: A cooling control system comprises a cooling apparatus having a refrigerant compressor, a vapor condenser, an expansion valve, an evaporator and a blower, a first temperature detection device for detecting a room temperature, a second temperature detection device for detecting a temperature of the refrigerant which is introduced into the evaporator, a detection device for detecting a temperature difference between a temperature of the refrigerant discharged from the evaporator and the temperature of the refrigerant introduced into the evaporator, and a control device for controlling operations of the compressor as well as the blower and for controlling an opening of the expansion valve in response to the detected inflowing refrigerant temperature, the detected temperature difference and the detected room temperature.