Hitachi, Ltd.

Hitachi Computer Engineering Co., Ltd.

Hitachi Computer Electronic Co., Ltd.

Masato Hirai

Ryozo Yoshino

Yoshinori Bekki

Toshihiko Nakauchi

Masami Kurata

Tomoaki Ishifuji

Masaaki Shida

Hidehiko Jusa

Hiroyuki Wada

Shigeo Nishita

Kenichiro Orita

Takaharu Aoyama

Sinzi Ikezawa

Teruo Moriguchi

A frequency-hopped mobile communication system is disclosed, in which a mobile wireless station automatically becomes a base station in accordance with the surrounding conditions, thereby automatically reconfiguring a communication network. A control frame is generated by at least one master station, and frequencies are hopped by a plurality of slave stations in accordance with the control frame. Each slave station switches the master thereof to be tracked, in accordance with the receiving conditions of the control frame and the relation between the control frame received from the master station and the status of the slave station and decides in which mode, master station or slave station, the slave station is to operate. The cells are thus automatically reconfigured.

Frequency-hopped wireless communication system and mobile wireless

A method of compensating a phase of a system clock for use in a system clock circuit for receiving an external clock to produce a system clock for an information processing system, in which the quantity of phase variation of the external clock supplied from a reference clock oscillator provided outside the system is detected; in accordance with the detected quantity of phase variation, the phase variation of the external clock supplied from the reference clock generator is compensated to supply the compensated external clock to the system clock circuit; whether or not a state of the external clock supplied from the reference clock oscillator provided outside the system is abnormal is detected; and in accordance with the detected state of the external clock, one of the external clock supplied from the reference clock oscillator and the compensated external clock is selected to supply the selected external clock to the system clock.

Method of compensating a phase of a system clock in an information

A method and apparatus for controlling the phase of a system clock, in which one of a first clock signal and a second clock signal is selected and output to a system as a system clock signal, the first clock signal being generated by a frequency synthesizer synchronized with an external clock signal supplied from a reference clock signal oscillator provided externally of the system, and the second clock signal being supplied from another reference clock signal oscillator provided internally of the system, and the phases of the first and second clock signals are controlled, prior to switching between the first and second clock signals and supplying the switched clock signal to the system as the system clock signal. The switching is delayed for a period while there is a phase shift between the first and second clock signal , when the system clock signal is switched between the first and second clock signal.

Method and apparatus for controlling phase of a system clock signal for

A PLL circuit for generating an AC output signal synchronized with an AC input signal applied thereto with a phase offset with respect to the input signal includes, in one embodiment, a charge pump circuit capable of varying the phase offset depending on the frequency of the AC input signal. In a signal transmission network system including a plurality of nodes coupled to a signal transmission line and distanced from one another by various repeat lengths of transmission path, each node has a repeater including such PLL circuit to suppress jitter caused by individual repeat length of transmission over the transmission line and still remaining in an equalized AC signal in each node.

Repeater and PLL circuit

A regenerative repeater for regeneratively repeating a signal to be transmitted is inserted in two ring-like transmission lines, and is provided with loop back means for automatically separating the regenerative repeater from the ring-like transmission lines in the condition that a power supply is in a not-yet-turned-on state, so that closed ring-like transmission lines are formed in the form where the regenerative repeater is removed in the condition that the power supply is in the not-yet-turned-on state.

Regenerative repeater

In a ring network system including two transmission lines transmitting a signal in directions opposite to each other, and a plurality of line concentrators connected in the form of a loop by the two transmission lines and each accommodating a plurality of terminal stations connected to one of the two transmission lines, a signal detecting unit and a terminating circuit are disposed in each of the line concentrators on the signal output side of each of the transmission lines so as to be connectable to and disconnectable from the transmission lines, so that, when the signal detecting unit in one of the line concentrators is connected to the associated transmission line, the transmission line is disconnected in the line concentrator, and the terminating circuit is connected to the downstream segment of the disconnected transmission line.

Ring network configuration

A multiplexer for trunking, over at least one high-speed trunk line on a multiplex basis under statistical time-division multiplexing control, transmission data on low-speed lines connected to a plurality of data terminal units, operates normally to transmit multiplexed data over leased high-speed trunk lines and, when a data buffer which temporarily stores data on the low-speed lines has its contents in excess of a certain level, operates by adding a public line as a high-speed trunking line to the leased high-speed trunk line for implementing the multiplexed data trunking.

Time division multiplexer with automatic call function

A relay circuit comprise first and second relays having respective terminals at which positive cross-talk of a signal of positive polarity is produced when the other terminals to which the positive polarity signal is applied are in the make and break states, respectively, and third and fourth relays having respective terminals at which negative cross-talk of a signal of negative polarity is produced when the other terminals to which the negative polarity signal is applied are in the make and break states, respectively, wherein with regards to the terminals where the cross-talk occurs, the first and fourth relays are connected to each other and said second and third relays are connected to each other, respectively.

Growing community of inventors

Hadano, Japan

Masato Hirai