Nec Corporation

Nippon Telegraph and Telephone Corporation

Kabushiki Kaisha Toshiba

K.k. Toshiba

Toshihiro Hara

Koji Ono

Akio Yotsutani

Yuji Ohta

Shoji Fuse

Noboru Saegusa

Ryoji Kawasaki

Shinji Kumataka

Kosuke Hashimoto

Kazuyuki Tate

Syoji Huse

Yukihiro Shimura

Yoshitoshi Murata

Hideki Toyama

Ichiro Tamura

Michimasa Shirakata

In a radio telephone apparatus of the TDMA/TDD system, signal transmission and reception are conducted by use of carriers having an identical frequency. This leads to a problem that the transmission intermediate frequency carrier and the transmission RF carrier enter the receiver section in an identical housing, thereby causing a cochanncl interference. To overcome this difficulty, there is disposed a frequency division modulator including a frequency divider for dividing by four a local signal having a frequency which is four times that of the intermediate frequency to obtain a carrier having a frequency shifted from that of the local signal by 90.degree.. Signal to be modulated is subjected to an orthogonal modulation according to the carrier wave to produce an intermediate frequency carrier. The operation of the modulator is stopped in a signal reception state to prevent the intermediate frequency carrier undergone the orthogonal modulation from being produced.

Quadrature modulator for TDMA/TDD radio communication apparatus

In a cordless key telephone system for servicing separate service zones (3.sub.1, 3.sub.2), a cordless station (5) establishes a two-way radio channel with an access unit (4) of the service zone in which it is located, and constantly monitors the field intensity of the established channel and transmits a zone switching signal when the field intensity is below a specified level as an indication that the cordless station is leaving a first zone (3.sub.1) and entering a second zone (3.sub.2). A main controller (2) establishes a switched connection between exchange lines (6) and the access units (4). In response to the zone switching signal from a given cordless station via the access unit of the first zone, the main controller holds an exchange line (6.sub.i) that is connected to the access unit (4.sub.j) of the first zone through a first switched connection, and establishes a second switched connection between the exchange line (6.sub.i) and the access unit (4.sub.j) of the second zone, instead of the first switched connection. A vocal announcement is applied to the exchange line indicating to a communicating party that the cordless station is switching zones.

Cordless key telephone system having zone switching function

In a service area of a mobile telephone system, there are plural base radio stations. A mobile radio station in the service area broadcasts a request signal of zone registration. All the base stations in the service area receive this request signal, measure the field intensity of the signal, and transmit the value of the measured intensity to the mobile radio station. The mobile radio station transmits a response signal to a base radio station where the field intensity is the highest. This response signal is reported to a radio channel control unit where the contents of the zone register is revised in accordance with the reported response.

Zone registration of a mobile in a mobile telephone system

In a cordless key telephone system for covering multiple service areas, access units are divided into groups corresponding respectively to the service areas, the access units of each group being located in the corresponding service area for broadcasting a recurrent sequence of address signals on a two-way radio control channel and carrying speech signals on an assigned two-way telephone channel. The access units of each group has a uniquely assigned control channel different in frequency from the control channel of the other group. Cordless stations are switchable to the control channel of a first group of the access units for detecting an address signal and subsequently switchable to the control channel of the access units of a second group if the address signal is not detected in a first sequence for detecting the addressed signal in a second sequence. A main controller is coupled to a switched telephone network for causing the access units to broadcast the address signals in response to an incoming call from the network and for establishing a connection between the network and one of the cordless stations.

Cordless key telephone system for covering multiple service areas having

A control method for a cordless telephone system including a main apparatus connected to a telephone line and having a line control function, a plurality of stationary apparatuses connected to the main apparatus and each having a radio transmitter/receiver, and portable telephones capable of communicating with the stationary apparatuses through a radio channel. When the main apparatus receives a simultaneous calling request signal from one portable telephone through a given stationary apparatus, it transmits a simultaneous calling request signal to whichever of the other portable telephones are not in use through corresponding stationary apparatuses. The main apparatus then receives, from that responding portable telephone through the corresponding stationary apparatus, an incoming call response signal including an extension number of the responding portable telephone which received the simultaneous calling request signal, and transmits a response display signal including that extension number to the portable telephone which requested simultaneous calling. The portable telephone which requested simultaneous calling displays the extension number of the responding portable telephone.

Control method for cordless telephone which displays identities of

A cordless telephone system comprises a radio telephone set and a connection unit connected to a wire telephone circuit and also connected to the radio telephone set through a radio communication circuit, for interconnection control between the wire telephone circuit and the radio telephone set. When the wire telephone circuit is put in an unusable state or a signal on the radio communication circuit is put in an unreceivable state, the connection unit transmits a disconnecting signal to the wireless telephone set to forcibly cut off the radio communication circuit.

Cordless telephone system

A cordless telephone having a base unit and a plurality of radio telephone sets. The base unit delivers a ringing signal from a telephone line to a radio telephone set which is in telephone communication with a remote subscriber coupled to the telephone network, and a receiving radio telephone set in accordance with a request for transfer by the transferring radio telephone set. If the receiving radio telephone set responds to the ringing signal and goes off-hook, the telephone communication is transferred to the receiving radio telephone set from the transferring radio telephone set. If the receiving radio telephone set does not respond or does not go off-hook, the transferring radio telephone set responds to the ringing signal and goes off-hook to carry on the telephone communication.

Cordless telephone apparatus and a method of controlling same

A cordless telephone system includes a connector connected to a subscriber telephone line and at least one radio telephone set through a radio channel to establish or hold a communication channel between the ratio telephone set and a subscriber. The connector includes a control unit incorporating a timer. The control unit sets the system in a self hold state in which the radio channel is kept connected or a complete hold state in which the radio channel is disconnected on the basis of a hold signal from the radio telephone set, the presence/absence of a radio reception signal within a predetermined period of time preset in the timer, and the type of reception signal.

A radio telephone system includes a base station connected to a telephone exchanger and a plurality of mobile stations connected to the base station through a radio channel including a control channel and communication channels. The base station includes a transmitter/receiver, a receiver, and a controller. In a stand-by mode, the controller sets a channel of the transmitter/receiver to the control channel to receive a calling signal from each mobile station and sets a channel of the receiver to a given communication channel to monitor vacancy of the communication channels.

Radio telephone system

An automatic gain control apparatus of the digital control type achieves fine control over the output amplitude of the gain controlled signal without increasing the number of bits handled by the A/D and D/A converters. The system operates by adding the output of a digital AGC converter to a variable step voltage which is set in response to the detected D.C. level of the signal to be gain-controlled.

Growing community of inventors

Tokyo, Japan

Toshihiro Hara