Other

Takeshi Fukuju

Toshihiko Umeda

Yoshiro Hasegawa

Disclosed is a telephone circuit in which two simultaneously available telephones are connected by use of a pair of twisted-paired cables. A PBX and a digital multi-function telephone are connected by a pair of twisted-paired cables, a digital signal channel of 2B&plus;D is established bidirectionally between the PBX and the digital multi-function telephone , and user information and a control signal are sent and received therebetween. The digital multi-function telephone and an analog telephone are connected by a pair of twisted-paired cables, and a signal is sent and received between the digital multi-function telephone and an analog telephone by an analog signal of a voice band and a DC/AC control signal. A B1-channel on a 2-wire digital line is allocated for user information transmission of the digital multi-function telephone , and a B2-channel is allocated for user information transmission of the analog telephone . A D-channel signal is shared by control signals of both the telephones. A bidirectional 2B&plus;D digital signal is sent and received by a proper transmission system such as a ping-pong transmission system.

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Yokohama, Japan

Takeshi Fukuju