Hitachi, Ltd.

Yagi Antenna Co., Ltd.

Kaoru Suda

Yukio Nakata

Osamu Shiotsu

Motoyoshi Morito

Matsuaki Terada

In a data signal demodulating circuit for demodulating data from a modulated signal burst in which a carrier signal is modulated by a data signal, noise elimination means is provided at at least one of the input and output of an AND circuit, to eliminate noise in periods during which there is no carrier present, by adding an output from a demodulator to an output from a carrier sense circuit, in order to completely eliminate noise occurring at the start and end of a demodulated data signal, and eliminate noise occurring during the rise time and fall time of the carrier sense circuit.

Demodulating circuit for data signal

In this data communication system, data communication is conducted through transmission lines between a plurality of stations. At each station, the presence of data to be sent is detected, the length of the detected data is measured, and that that station is disconnected from the transmission lines when the length of data exceeds a predetermined value, to inhibit the sending of data from that station.

Method and device for data communication

A method for data communication usable for a system having a common transmission line, a plurality of transceivers connected to the common transmission line, and a data processing equipment connected to each of the transceivers, the system being arranged such that data from the data processing equipment is sent to the common transmission line through the corresponding transceiver, while data from the common transmission line is sent to the data processing equipment through the corresponding transceiver, thereby effecting a data communication between data processing equipment, wherein when a request to send data is sent from the data processing equipment to the corresponding transceiver, a carrier signal is sent to the common transmission line, and when the fact that no data is sent from any of the other transceivers to the common transmission line is detected during a given period of time after the sending of the carrier signal, the transceiver gives a permission to send data, to the corresponding data processing equipment, which then sends data on the permission. Also disclosed is a device for carrying out the above-mentioned method for data communication.

A data communication system including reflectors having first light emitting elements for radiating light and first light receiving elements for receiving light, a plurality of transceivers disposed confronting said reflectors and having second light emitting elements for radiating light and second light receiving elements for receiving light, and a data processing unit to be connected to the transceivers, wherein light corresponding to the data to be transmitted from the data processing unit is converged and radiated from the second light emitting element of the transceiver to the reflector, the light from the transceiver is received by the first light receiving element of the reflector, light corresponding to the data thus received is radiated from the light emitting element of the reflector to all of the transceivers confronting said reflector and is received by the second light receiving elements of the transceivers, and the data thus received is sent to the data processing unit.

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Ohmiya, Japan

Kaoru Suda