Fujitsu Corporation

Yutaka Suzuki

Yuji Maeda

Takeshi Uehara

Shigehiko Yazawa

Masaharu Matsumoto

Atsuo Serikawa

Yoshiaki Inoue

Umihiko Moteki

Michihiro Hamada

Yoshihide Morimoto

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

A digital telephone set includes a digital telephone circuit and an emergency analog circuit. Normally, the digital telephone circuit is made active so that a handset provided in common therewith is connected to a digital transmission line. In an emergency, the emergency analog circuit is made active instead of the digital telephone circuit so that the handset is connected to an analog transmission line. A dial key pad unit and a speaker are provided in common with the digital telephone circuit and the emergency analog circuit.

Digital telephone set having an emergency switching function and

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Yokohama, Japan

Yutaka Suzuki