Abstract: A multi-channel optical communication system includes an optical transmitting apparatus and an optical receiving apparatus. The optical transmitting apparatus has a retroreflector and a modulator for modulating light reflected by the retroreflector according to a transmission signal. The light receiving apparatus has a light source and a demodulating circuit for demodulating the transmission signal modulated by the modulator from the light emitted from the light source and reflected from the retroreflector. The modulator includes a plurality of optical reflection devices arranged on a reflection plane of the retroreflector and capable of controlling optical reflection independently of each other and a circuit for separately controlling each of the optical reflection devices. The demodulating circuit includes a CCD having a plurality of photoreceptors arranged correspondingly to the arrangement of the optical reflection devices.

Abstract: A telephone terminal includes: a first radio frequency communication unit; a second radio frequency communication unit that communicates through a weak wave; an optical communication unit; a telephony unit; a first switch that selectively couples the first or the second radio frequency communication unit to the telephony unit in response to an externally applied command; a incoming call detecting circuit connected to the first switch; and a second switch that selectively enables communication by the telephony unit through the first radio frequency communication unit or the optical communication unit in response to an incoming call detected by the incoming call detecting circuit, depending on the status of the first switch.

Abstract: A telephone regulation system to regulate usage of a telephone terminal that carries out conversation using a radio wave includes an approach recognition device provided at the neighborhood of an approach path to a predetermined region to transmit a first command through a weak wave to a portable telephone terminal passing through the neighborhood and entering the predetermined region, and a departure recognition device provided in the neighborhood of a departure path from the predetermined region to transmit a second command through a weak wave to a telephone terminal passing through the neighborhood and departing from the predetermined region.

Abstract: A multi-channel optical communication system includes an optical transmitting apparatus and an optical receiving apparatus. The optical transmitting apparatus has a retroreflector and a modulator for modulating light reflected by the retroreflector according to a transmission signal. The light receiving apparatus has a light source and a demodulating circuit for demodulating the transmission signal modulated by the modulator from the light emitted from the light source and reflected from the retroreflector. The modulator includes a plurality of optical reflection devices arranged on a reflection plane of the retroreflector and capable of controlling optical reflection independently of each other and a circuit for separately controlling each of the optical reflection devices. The demodulating circuit includes a CCD having a plurality of photoreceptors arranged correspondingly to the arrangement of the optical reflection devices.