Fujitsu Corporation

Masaru Asahara

Takuro Oguchi

Shunroku Sasaki

Hiroshi Nakamura

Ryushiro Yoshizawa

Noriyasu Toyonaga

Hiroaki Ohyama

A mobile communication system includes an exchange, a plurality of radio base stations coupled to the exchange, and a plurality of mobile stations. The exchange includes a device for obtaining receivable periods of the mobile stations, which are continuously maintained in a call receivable state during the receivable periods, a device for determining whether the mobile stations are busy and a decision device which sequentially sends call signals to the mobile stations to determine whether or not each of the stations responds to a call signal. The results of determination by the decision device are recorded in a recording device.

Mobile communication system

A radio communication adapter is used in a mobile communication system including a first mobile communication network, first mobile stations registered in the first mobile communication network, a second mobile communication network connected to the first mobile communication network, and second mobile stations registered in the second mobile communication network. The radio communication adapter is attached to one of the second mobile stations. The radio communication adapter includes a radio communicating part for communicating, via a radio channel, with the first mobile stations located outside a first service area of the first mobile communication network, and a requesting part for requesting that first identification data of the first mobile stations located outside the first service area is registered, in connection with the second mobile stations, in the first mobile communication network via the above-mentioned one of the second mobile stations and the second mobile communication network.

Radio communication adapter connected to mobile station and mobile

A portable telephone system includes a first telephone network including a terminal station, a first telephone set connected to the first telephone network via the terminal station, a second telephone network including a communication center which is connected to the first telephone network at a connection point, and at least one second telephone set registered in the communication center and connected to the first telephone network via the terminal station. The second telephone set is a portable telephone set having a base station part and a portable station. The communication center includes a first part for sending a line hold signal to the first telephone set via the first telephone network when a call to the portable station of the second telephone set is received via the first telephone network, and a second part for sending control information to the base station part of the second telephone set, where the control information includes a notification that a call is made to the portable station of the second telephone set from the first telephone set and a telephone number of the first telephone set. The base station part of the second telephone set includes a third part for dialing the telephone number of the first telephone set in response to the control information received from the communication center, so that a service connection is made, after the third means dials the telephone number of the first telephone set, between the first and second telephone sets via the terminal station of the first telephone network.

Portable telephone system having selectable bypass line

Band pass filter circuit for a band pass filter which detects a phase difference between input and output signals of said band pass filter, and the detected output controls, via a low pass filter, a voltage controlled oscillator, the output of which controls first and second mixers connected respectively to an input side and an output side of the band pass filter, so that the output of the first mixer can be maintained at the center frequency of said band pass filter. Further, when an irregularly timed signal is received, before an input signal is pulled in the synchronized state, said band pass filter is provided with a wide pass band so as to pull the signal in the synchronized state in rapidly. After said input signal is pulled in said center frequency, the pass band of said band pass filter is changed to a narrow bandwidth so as to improve the quality of the noise and at the same time, a cutoff frequency of said low pass filter is changed to a lower frequency side so as to improve the stability of the band pass filter circuit.

Growing community of inventors

Kawasaki, Japan

Masaru Asahara