Hitachi, Ltd.

Hitachi Denshi Kabushiki Kaisha

Hitachi Engineering Co., Ltd.

Kazuhiko Takaoka

Yasushi Yokosuka

Yasuyuki Kozima

Yasuhiro Kita

Kohei Ishizuka

Narimichi Maeda

Yoshiro Kokuryo

Masahiro Koya

Kozo Nakamura

Yasuyuki Kojima

Yukihito Ishihara

Takeshi Asai

Kagehiro Yamamoto

Takeshi Shimanuki

A high-speed image signal processing system for encoding an image signal, read out at a high speed, into an encoded signal, and/or for recording a decoded signal obtained through a decoding operation on an encoded signal. The image signal, obtained through a scanning operation on an original document, is sent to an encoder through an image bus. A code bus, provided at an output of the encoder, is connected with an encoded-signal memory for storing the encoded signal. A code transfer unit, for performing input/output operation over the encoded signal and for performing transfer of the encoded signal from the code bus to a system bus, is disposed between the code bus and the system bus. A control unit, performing control over the entire system, and a document management data memory, storing management data for performing management over documents stored in the encoded-signal memory, are connected to the system bus. Further, the control unit, when receiving a request from a data input/output unit, issues a command indicative of the start of the encoding/decoding operation to the encoder/decoder. The encoder/decoder, when receiving the command from the control unit, sequentially processes the data from the data input/output unit without any intervention of the control unit, and when the data processing is completed, informs the control unit of the end of the data processing.

High-speed image signal processing system

In a MODEM having modulation and demodulation circuits and a circuit for controlling the modulation and demodulation, a modulator-demodulator apparatus includes a register for accepting a macro-instruction from an external source; a circuit for interpreting and executing the macro-instruction; and a circuit for outputting a response to the macro-instruction, whereby the MODEM is controlled in response to the macro-instruction accepted from the outside source. The modulator-demodulator apparatus is suitably integrated over a single semiconductor substrate.

Modulator-demodulator apparatus and system

A first phase control loop not including a signal delay part and a second phase control loop including a signal delay part such as an automatic equalizer are formed independently of each other in a demodulator incorporated in a MODEM. The first and second phase control loops are arranged in such a relation that an input to the second phase control loop is not affected by an output of the first phase control loop, so that correction of a frequency offset by the first phase control loop and correction of a frequency jitter by the second phase control loop can be carried out independently of each other. This arrangement facilitates the design of the first and second phase control loops and improves the stability of the phase control system.

Phase control device

A demodulator for facsimile equipment in which there is provided a memory for storing equalizer coefficients of an automatic equalizer and a divergence detector for detecting divergence of the automatic equalizer, and in which equalizer coefficients of the automatic equalizer established at the beginning of transmission or reception are stored in the memory. In the event of divergence of the automatic equalizer during reception of a subsequent picture data message, the stored equalizer coefficients are re-set in the automatic equalizer.

Demodulator for facsimile equipment

In a gain control circuit, an electric power calculating circuit is connected to a variable gain amplifier and a gain setting circuit for generating a gain control signal applied to the variable gain amplifier to control the gain thereof.

Electric power detecting circuit and gain control circuit using the same

An equalizer apparatus suitable for use in a MODEM for receiving a signal having passed through a number of carrier-band lines is disclosed in which the number of carrier-band lines is detected from a training signal, and electrical connection of a fixed equalizer to a variable equalizer is controlled on the basis of the number of carrier-band lines, in order to form a precise, simple automatic equalizer apparatus.

Automatic equalizer apparatus

A multi-frequency signal receiving apparatus for receiving signals with at least more than two frequencies and selectively separating these signals, comprising a first maximum value detecting means for detecting the maximum value of the rectified outputs of a plurality of channel filters provided for said signals to be selected; a second maximum value detecting means for detecting the maximum value of the rectified outputs at the intermediate stage of two channel filters for discriminating the signals at both ends of the signal frequency bands of a plurality of said channel filters; and a comparison means for comparing the outputs of said first and second maximum value detecting means with an appropriate weight and thereby detecting the presence or absence of the signal to be detected; whereby based on the result of comparison, the threshold value of discriminators placed at the succeeding stage of said channel filters for discriminating the predominant frequency signal is controlled. The invention thus permits the elimination of input filers, and realizes an economical and reliable signal receiver.

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Yokohama, Japan

Kazuhiko Takaoka