Fujitsu Corporation

Atsuo Serikawa

Takaya Yamamoto

Kenji Takato

Yuji Maeda

Masaharu Matsumoto

Kiyoshi Shibuya

Mitsutoshi Ayano

Yoshimi Iijima

Takayuki Ogawa

Kenichi Ogawa

Yasuhiro Saito

Takeshi Uehara

Shoji Nojiri

Koji Yano

Keiichi Otani

Umihiko Moteki

Yutaka Suzuki

Yasuo Miyazaki

Kiyoshi Kasahara

Satoshi Kasuya

Yoshihide Morimoto

A TDMA in a CATV center and a CAU in a subscriber home communicate a B-ch idle/busy map indicating the idle/busy state of a B channel in synchronization with each other, so that the allocation of the B channel dedicated to sound and the C channel dedicated to data in a transmission frame can be dynamically changed according to the contents of the B-ch idle/busy map. Consequently, it becomes possible to effectively use a transmission bandwidth up to its maximum.

Sound/data sharing communications system

The present invention relates to a time division multiple access communication technique. A center unit for time division multiple access communications with a plurality of subscriber units comprises a channel receiving section for receiving a synchronization establishing signal with a variable receive timing, from each of the subscriber units as a varying channel signal and further for receiving, as a fixed channel signal, a communication signal from the synchronization established subscriber's unit at a constant timing, and a control section for controlling the receive processing in the channel receiving section so that the varying channel signal is receivable within a period for receiving the fixed channel signal.

Time division multiple access communication system, signal receiving method in time division multiple access communication system, and center unit for use in time division multiple access communication system

A communication-line-quality measuring system includes transmission and terminal equipment. Transmission equipment has a first frame assembling part transmitting a down-link multiplexed frame signal to a down-link line having a first frequency, and a first frame disassembling part disassembling an up-link multiplexed frame signal transmitted through an up-link line having a second frequency. Terminal equipment has a second frame disassembling part disassembling the down-link multiplexed frame signal, and a second frame assembling part transmitting the up-link multiplexed frame signal obtained by frame-multiplexing an output signal of the subscriber unit with a control signal, to the up-link line. A pattern generation part in the first frame assembling part provides a test signal to an available channel of signal frames in the down-link multiplexed frame signal. A loop-back part between the second frame disassembling part and the frame assembling part loops back the test signal derived from the down-link multiplexed frame signal in the second frame disassembling part to the second frame assembling part. The second frame assembling part provides the test signal in the up-link multiplexed frame signal to transmit to the transmission equipment. A comparing part in the transmission equipment compares the test signal in the up-link multiplexed frame signal, which is looped back by a control of the loop-back part, with a reference signal the same as the test signal generated in the pattern generation part.

Communication-line-quality measuring system using a conventional signal

A method of an automatic adjustment of a carrier level is used for a system having a center device, a communication line extending from the center device, and at least one communication-terminal device connected to the communication line. The system conducts two-way communication of data signals on the communication line based on a predetermined multiplexing scheme. The method includes the steps of periodically transmitting a carrier-level-measurement message from the center device to the communication line for each high-frequency channel used for the two-way communication, the carrier-level-measurement message being sent via a first channel different from channels used for communication and control, transmitting a reply message in response to the carrier-level-measurement message from a communication-terminal device to the center device via a second channel different from the channels used for communication and control, transmitting a carrier-level-adjustment message from the center device to the communication line via the first channel, the carrier-level-adjustment message containing level-adjustment information based on a carrier level of the reply message received by the center device, and adjusting a carrier level of the communication-terminal device based on the level-adjustment information of the carrier-level-adjustment message received by the communication-terminal device.

Method and device for two-way communication network

In a calling signal transmitting apparatus, a ring trip equipment, including a ring trip detecting circuit for detecting a ring trip signal in response to an off-hook operation of the telephone set during a signal state of an intermittent ringing signal and a loop detecting circuit for detecting a loop signal in response to an off-hook operation of the telephone set during a nonsignal state of the intermittent ringing signal. Also included are a logical OR gate circuit, for providing, as a status signal, a logical sum of the ring trip signal and the loop signal, and a supervising circuit for supervising the status signal. When an incoming call is being received by the telephone set, when the supervising circuit detects an off-hook state in the status signal, the supervising circuit stops the transmission of a ringing signal to the telephone set, and carries out a second supervising operation for supervising the status signal, and, if an on-hook state is detected during the second supervising operation, said supervising circuit again transfers the ringing signal to the telephone set.

Calling signal transmission apparatus

A battery feed circuit for a subscriber line includes first and second feed circuit parts, each supplying a constant current to a corresponding subscriber line. The first and second feed circuit parts are provided with at least one of a common mode noise suppressor and a power source noise suppressor. The common mode noise suppressor includes first and second reference voltage output circuits and an intermediate voltage output circuit to produce the voltage between the first and second subscriber lines and superpose the same onto the first and second reference voltages. The power source noise suppressor functions to cancel the power source noise voltage at the output, of the first and second feed circuit parts.

Battery feed circuit for subscriber line

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Tokyo, Japan

Atsuo Serikawa