Abstract: A data communication system is provided in which a time required for a wiretapper to decrypt an encrypted text is significantly increased so that concealment is improved. In a data transmitting apparatus (17105), a multilevel encoding part (111) switches a plurality of key information to generate a multilevel code sequence in which the average values of signal levels are different, and then combines the generated multilevel code sequence with information data to generate a multilevel signal having a level corresponding to the combination of the two signal levels. A light modulating part (125) converts the multilevel signal into a modulated signal of a predetermined modulation scheme and transmits it. In a data receiving apparatus (17205), a light demodulating part (219) demodulates the received modulated signal into the multilevel signal.

Abstract: A data communication apparatus which improves security against eavesdropping is provided for secret communication using Y-00 protocol. A multi-level code generation section 111 generates, based on key information 11, a multi-level code sequence 12 in which a signal level changes so as to be approximately random numbers. A level conversion section 113 irreversibly converts the multi-level code sequence 12 such that a converted multi-level code sequence 19 does not constitute a mapping of the multi-level code sequence 12. A multi-level processing section 112 generates a multi-level signal 13 having a plurality of levels each corresponding to a combination between the information data 10 and the multi-level code sequence 12. A modulator section 114 modulates a multi-level signal 14 in a predetermined modulation method and outputs a modulated signal 15.

Abstract: An optical SSB-SC modulation section 13 subjects an optical signal fa outputted from an optical source 11 to an optical SSB-SC modulation based on the amplitude of an external electric signal fc to thereby output an optical intensity-modulated signal. An optical phase modulation section 14 subjects the optical signal fa to an optical phase modulation based on the amplitude levels of the first to nth external electric signals having frequencies f1 to fn to thereby output the resultant signal as an optical phase-modulated signal. An optical combining section 15 combines together the optical intensity-modulated signal and the optical phase-modulated signal. An optical detecting section 16 performs an optical homodyne detection through a squared detection of the optical intensity-modulated signal and the optical phase-modulated signal combined together to thereby produce a wideband modulated signal, being the difference beat signal between the two optical signals.

Abstract: A data communication system wherein the concealment is enhanced by significantly increasing the time required for the wiretapper to decrypt a cipher text. The data communication system is constituted by connecting a data transmitting apparatus (13105) to a data receiving apparatus (11201) via a transmission path (110). In the data transmitting apparatus (13105), a multilevel encoding part (111) receives a predetermined first initial value (key information) and in formation data and generates a multilevel signal that varies in level substantially in a random number manner. A dummy signal superimposing part (118) superimposes a dummy signal on the multilevel signal. A modulating part (112) converts the multilevel signal to a modulated signal of a predetermined modulation form and transmits the modulated signal.

Abstract: A data communication apparatus wherein the stealthiness has been enhanced by significantly increasing the time required for a wiretapper to decrypt an encrypted text. The data communication apparatus is constituted by connecting a data transmitting apparatus and a data receiving apparatus via a transmission path. The data transmitting apparatus receives a first predetermined initial value (key information) and information data, generates a multi-valued signal the level of which varies substantially like a random number, and converts the multi-valued signal to a modulated signal of a predetermined modulation format for transmission. The data receiving apparatus demodulates the modulated signal to output the multi-valued signal, and then reproduces the information data from the multi-valued signal and a second predetermined initial value (key information) that is received.

Abstract: An optical transmission system including an optical transmitting device and an optical receiving device. The optical transmitting device includes a data signal splitting section for splitting data signal information into at least two parts and generating at least two electrical signals having different center frequencies and bands, a frequency multiplexing section for performing frequency multiplexing for the at least two electrical signals, and an electrical-to-optical conversion section for converting the frequency-multiplexed signal to an optical signal and sending it to an optical transmission path. The optical receiving device includes an optical-to-electrical conversion section for converting the optical signal to a frequency-multiplexed signal, a band demultiplexing section for demultiplexing the frequency-multiplexed signal to obtain at least two electrical signals, and a data signal recovering section for recovering the data signal based on the at least two demultiplexed electrical signals.

Abstract: A method of manufacturing of power transmission chain 1 by interconnecting plural link plates 2 with pins 3. Individual pin pairs 3 are arranged and temporarily fixed to places. The link plates 2 are sequentially stacked in layers by press-fitting respective through-holes 4 of the link plates 2 about the respective pin pairs 3, whereby the link plates 2 are interconnected to form a circular chain (an endless loop). Subsequently, the individual pin pairs 3 are released from the temporarily fixed state. Thus, the manufacture of the power transmission chain 1 is decreased in the number of operation steps, so that the chain may be assembled easily.

Abstract: Manufacture method and manufacturing apparatus for power transmission chain according to the invention are adapted to accomplish exact positioning of pin members and link plates. This permits the pin members to be positively press-inserted into pin holes of the link plates and hence, the fabrication of the power transmission chain is facilitated.

Abstract: The ultra wideband communication system comprises: a pulse generation section for generating a pulse signal based on a data signal; a first optical phase modulation section for performing optical phase modulation in accordance with the pulse signal, and outputting a resultant signal as an optical pulse signal; an optical transmission path for propagating the optical pulse signal; a template generation section for outputting a template signal; a second optical phase modulation section for performing optical phase modulation on the optical pulse signal in accordance with the template signal, and outputting a resultant signal as an optical phase demodulation signal; an optical phase intensity conversion section for converting information about an optical phase of the optical phase demodulation signal into information about an optical intensity thereof, and outputting a resultant signal as an optical correlation signal; an optical-electrical conversion section for performing optical-electrical conversion on the o

Abstract: A data communication apparatus which causes the eavesdropper to take a significantly increased time to analyze a cipher text and provides high concealability is provided. In a modulator section 112a, a branching section 114 branches a lightwave 20 outputted from a light source 113, and outputs respective branched lights to a first light path 117 and a second light path 118 respectively having different light path lengths. A light modulator section 116 modulates, based on a multi-level signal 13, a lightwave propagating at least one light path of the first light path 117 and the second light path 118. An interference section 119 causes the lightwaves outputted from the first light path 117 and the second light path 118 to interfere with each other, and outputs such interfered lightwave as a modulated signal 14.

Abstract: A highly concealable data communication apparatus which is based on an astronomical complexity and causes an eavesdropper to take a significantly increased time to analyze a cipher text, is provided. In a multi-level code generation section 111a, a random number sequence generation section 141 generates, based on predetermined key information 11, a plurality of modulation pseudo-random number sequences. The plurality of modulation pseudo-random number sequences is inputted to a multi-level conversion section 142 as a part of an input bit sequence which is converted into a multi-level code sequence 12. A multi-level processing section 111b combines the multi-level code sequence 12 and information data 10, and generates a multi-level signal 13 having a plurality of levels corresponding to a combination of the multi-level code sequence 12 and the information data 10.

Abstract: A data transmitting apparatus 1101 generates, by using predetermined first key information 11; and information data 10, a multi-level signal 13 in which a signal level changes so as to be approximately random numbers, and converts the multi-level signal 13 into a modulated signal 14, in a predetermined modulation method and transfer the same. A data receiving apparatus 1201 demodulates the modulated signal 14 so as to be converted into a multi-level signal 15, and reproduces information data 18 from the multi-level signal 15, using second key information 16 which has the same content as first key information 11 used by the data transmitting apparatus 1101.

Abstract: A data communication apparatus which causes the eavesdropper to take a significantly increased time to analyze a cipher text and provides high concealability is provided. A multi-level code generation section 111a generates, based on predetermined key information 11, a multi-level code sequence 12 in which a signal level changes so as to be approximately random numbers. A multi-level processing section 111b combines the multi-level code sequence 12 and information data 10, and generates a multi-level signal 13 having a plurality of levels corresponding to the combination of the multi-level code sequence 12 and the information data 10. A modulator section 112 treats the multi-level signal a predetermined modulating processing and generates a modulated signal.

Abstract: A data communication apparatus 1 for safely transmitting information data 11 and additional information 14 is provided. In a data transmitting apparatus 101, a random number sequence generating part 111 generates a random number sequence 12 from key information 11. A diffusing part 112 generates diffused additional information 14 by time-diffusing additional information 14. A multi-level signal generating part 113 generates a multi-level signal 16 the signal level of which varies substantially like a random number, based on information data 13, the random number sequence 12, and the diffused additional information 14. In a data receiving apparatus 201, a random number sequence generating part 211 generates a random number sequence 22 from key information 21. An information data decoding part 213 decodes information data 23 and additional information 24 based on the random number sequence 22.

Abstract: A power transmission chain of the invention includes: plural link plates individually including through-holes and arranged in a chain advancing direction and a chain widthwise direction and with predetermined spacing; and plural pins inserted through the through-holes for flexibly interconnecting the link plates. Since the link plates are arranged in the chain widthwise direction with the predetermined spacing, a respective pair of adjoining link plates are prevented from coming into friction contact with each other during the operation of the power transmission chain. Hence, the power transmission chain may be prevented from suffering the decrease of power transmission efficiency.

Abstract: The present invention provides a low-cost optical transmission system using a plurality of subscriber lines which is capable of efficiently utilizing an optical transmission path. A communication status observing section 116 in a transmitting device 1 classifies subscribers into a plurality of groups based on a communication status at each subscriber end, and outputs constellation level information and level information which are different for each group. For each constant cycle, a modulation control section 117 and a gain control section 118 respectively set a QAM constellation level and a signal level which are different for each group and used in a basic modulating section 103.

Abstract: An optical transmission module and method are capable of suppressing the occurrence of multiplexed reflection light, thereby making it possible to easily carry out an optical coupling operation at low cost. A loss generator having an attenuation factor determined based on an extinction ratio of a modulation signal is provided to attenuate reflection light in a transmission path, thereby making it possible to provide a low-cost optical transmission module, which ensures a practically satisfactory efficiency, without providing an optical isolator component. Also, in the optical transmission module, the intensity of light is adjusted by the loss generator. Thus, it is possible to realize the optical transmission module using an optical mounting technique with such accuracy as employed for an ordinary module.

Abstract: Modulators respectively modulate baseband signals into IF signals having different frequencies. A multiplexer multiplexes the IF signals. An electrical-optical converter intensity modulates the multiplexed IF signals into optical signals. A local oscillation signal source outputs a predetermined local oscillation signal. An external modulator intensity-modulates the optical signal using the local oscillation signal. An optical branching portion branches the intensity-modulated optical signal and respectively outputs branched optical signals to radio base stations. An optical-electrical converter converts the optical signal into an electric signal, to obtain an RF signal by frequency-converting the IF signal. An antenna only transmits a component having a desired radio frequency extracted in a band filter from the RF signal to a subscriber terminal.

Abstract: There are provided a device and a method for assembling a tapered roller bearing, which allow even a tapered roller having a large taper angle to be easily assembled to a pocket of a cage. The tapered roller 35 is inserted into the pocket 33 with the larger-diameter side of the tapered roller 35 in the lead from the inner side of the cage 30 and moreover from the smaller-diameter annular portion side of the cage 30, by which the tapered rollers 35 are assembled to the cage 30.

Abstract: In an optical transmission system, a multiplexer frequency-division-multiplexes a plurality of signals, and outputs the resultant signal to an FM modulator. The FM modulator converts the frequency-division-multiplexed signal into an FM modulated signal through frequency modulation using the frequency-division-multiplexed signal as an original signal. A frequency-divider converts the FM modulated signal into a frequency-divided FM modulated signal whose frequency is ½n (n is an integer of not less than 1) the frequency of the FM modulated signal. An optical modulator has a predetermined input-voltage vs. output-optical-power characteristic, and is biased at the minimum point (voltage) about the output optical power. The optical modulator modulates an unmodulated light fed from a light source with the applied frequency-divided FM modulated signal to produce an optical signal whose optical carrier component is suppressed, and sends the optical signal to an optical transmission line.