Iwatsu Electric Company Ltd.

Iwasaki Tsushinki Kabushiki Kaisha

Nippon Telegraph and Telephone Corporation

Yoshihiro Kawata

Toshimichi Shimatani

Masayuki Kawashima

Hideharu Omori

Masaharu Kamigaki

Akira Hirato

Hiroyuki Miyashita

Yuji Kondo

Masayuki Ito

Teruo Matsufuji

Nobuyasu Shiga

Teruyuki Kubo

Hironobu Oshikata

Naoyuki Yamaguchi

Koichi Ichimura

Tetsuro Inomata

Tsunetaka Sakata

Kansei Iwata

A synchronizing system in a digital communication line comprises a plurality of local switches for storing at least one digital line and monitoring a first piece of busy information when a clock source is already present, the local switches, if a first new clock source occurs while the first busy information is indicating no busy state, being capable of transmitting a master right request to turn the busy information to the busy state and to specify the first new clock source as a master clock and, on receiving a master right specification with respect to the master right request, being capable of outputting the first new clock source as the master clock; and a master switch connected to the plurality local switches in a star manner, by a link transmission line for transmitting control information including the master clock, master right request and master right specification, for monitoring a second piece of busy information indicating a busy state, the master switch, if a second new clock source occurs while the second busy information is indicating no busy state, being capable of transmitting the second new clock source as a master clock and, if the second new clock source competes with the first new clock source in the local switches that has output the master right request, being capable of arbitrating the competition between the first and second new clock sources and selecting one of the clock sources to turn the busy information to the busy state and, if the first clock source is selected, outputting the master right specification to the local switches that have transmitted the master right request.

Synchronizing system in digital communication line

A key telephone system for use in PCM telecommunications includes an office line communication units, an extension interface unit, a receiving unit, an extension communication unit, and an information transmitting and receiving unit. The system further includes a timing setting unit for setting the timings for transmitting and receiving information from and to each of the office line communication unit, the extension interface unit, the receiving unit, the extension communication unit, and the information transmitting and receiving unit in which downstream information, which is applied from the extension interface unit to a plurality of terminal units, contains a start bit, bits expressive of data information, and bits expressive of parity information in each of a plurality of frames, contains bits expressive of control information in at least one of the frames, and contains frame-synchronization information for achieving the synchronization of frames in at least one of the frames, and upstream information, which is applied from the terminal units to the receiving unit, contains the bits expressive of the data information, the bits expressive of the parity information, and the bits expressive of the control information, and one of the downstream and upstream information is sent in the former half of each of the frames, and the other thereof is sent in the latter half thereof.

Key telephone system

There is disclosed a data circuit-terminating equipment (DCE) which connects a start-stop synchronous data terminal equipment (DTE) which is not synchronized with a PCM transmission line having various speeds. Further the DCE can satisfy recommendations of the V25 bis of CCITT. The DCE includes a start-stop synchronizing circuit to deliver a sampled request-to-send signal RS, a sampled send data and to transmit a clear-to-send signal CS to the DTE, a PLL obtaining a clock from the line, a timing generator generating timings for circuits, a mapping circuit mapping to make the sampled send data match into the line speed, a sending register converting transmission speed of the mapping circuit output to send to the line at the instructed period, a receiving register receiving data from the line to deliver data with the required speed during the required period for the DTE, and a demapping circuit receiving the receiving register output to demap and send to the DTE. In the DCE satisfying the recommendations, the demapping circuit ANDs a clear-to-send signal and bits indicating the synchronized state to send the clear-to-send signal, and a short line shorting the clear-to-send signal and a carrier detect signal is employed.

Data circuit-terminating equipment

There is disclosed a data circuit-terminating equipment (DCE) which connects an asynchronous data terminal equipment (DTE) with a PCM trnsmission line having various speeds. Further the DCE can satisfy recomendations of the V25 bis of CCITT. The DCE includes a PLL obtaining a clock from the line, a timing generator generating timings for circuits, a mapping circuit mapping to make data from the DTE match into the line speed, a sending register converting transmission speed of the mapping circuit output to send to the line at the instructed period, a receiving register receiving data from the line to deliver data with the required speed during the required period for the DTE, and a demapping circuit receiving the receiving register output to demap and send to the DTE. In the DCE satisfying the recommendations, the demapping circuit ANDs a clear-to-send signal and bits indicating the synchronized state to send the clear-to-send signal, and a short line shorting the clear-to-send signal and a carrier detect signal is employed.

CMI code has many features, but the interference on a transmission line resulted from radiant noise is an unavoidable problem. In the invention, WALSH 1 code is employed to solve the problem. Clock pulses having a frequency twice that of code on a transmission line in the WALSH 1 code are extracted. The extracted clock pulses consists of zero phase clock pulses and pi phase clock pulses, wherein the zero phase clock pulses are accurately extracted. An embodiment comprises an clock extraction circuit for extracting extracted clock pulses of 2f.sub.0 from a receive pulse train of frequency f.sub.0, a latch circuit for latching the receive pulse train with the extracted clock pulses, a frame synchronizing circuit for obtaining frame pulses synchronized with the extracted clock pulses from the latched output pulses, a zero phase separation circuit for obtaining zero phase clock pulses from the extracted clock pulses and the frame pulses, and a regenerative discrimination circuit for obtaining a regenerated pulse train from the zero phase clock pulses and the latched output pulses. The regenerated pulse train has the same pattern as that of the original code from which the receive pulse train is converted by the WALSH 1 code.

Digital synchronizing circuit

A data transmission circuit is disclosed which is arranged so that when transmitting data and control signals of a terminal equipment accommodated in a transmission line of 64 Kbps channels through use of a multi-frame arrangement, the data is assigned to a required number of bits in a predetermined number of frames in the multi-frame or adjacent ones of the predetermined number of bits and at least one synchronization flag bit and various control signals are assigned to the remaining bits but a request to send signal and the synchronization being assigned to one of the remaining bits according to the logic OR of their succeeding sampled values, whereby data of different transmission speeds can be transmitted by the same circuit.

Data transmission circuit

A click tone removing system for a time division switching system which performs switching of speech channels by a highway switch inserted in a highway. When a hook information detector and a dial information detector detect hook information and a dial information, respectively, delivery of a PCM speech sending signal to the highway is prevented by a blocking function for a fixed period of time, so that the highway is controlled to switch the speech channel, thereby removing a click tone generated by dialing. A subscriber's circuit of an exchange, which changes over a speech sending highway and a speech receiving highway by means of a highway switch, is characterized by the provision of an A/D converter for digitizing a speech sending signal to a digitized speech sending signal sent out to the speech sending highway, a D/A converter for converting a digitized speech receiving signal applied from the speech receiving highway into an analog signal, a gate for gating the input signal to the D/A converter, and a control circuit for controlling the gate, so that during real time processing the speech receiving signal highway is interrupted by opening and closing the gate without controling the higway switch.

Subscriber's circuit for time division switching system

A transmission system for a key telephone system, in which speech signals and control signals are transmitted through two pairs of transmission conductors between a key service unit and each of a plurality of key telephone sets, and in which DC electric power is supplied from the key service unit to each of a plurality of telephone sets. In accordance with the present invention, the speech signal and the control signal are transmitted through a first transmission line of high frequency band provided by one pair of the transmission conductors from the key telephone set to the key service unit, and the speech signal and the control signal are transmitted through a second transmission line of high frequency band provided by the other pair of the transmission conductors from the key service unit to the key telephone set. A third transmission channel is provided by the use of respective neutral points of the two pairs of transmission conductors established at the key service unit and by the use of respective neutral points of the two pairs of transmission conductors established at the key service unit to form a voice-frequency two-way transmission line between the key service unit and the key telephone set. DC electric power is supplied from the key service unit to the voice-frequency two-way transmission line from a DC power source, so that the DC electric power supplied is separated from the voice-frequency two-way transmission line by a power separating circuit, such as a smoothing circuit.

Key telephone transmission system

In display apparatus wherein a picture image corresponding to an information train given by an electronic computer is written in a storage tube by a random scanning system and then the picture image is repeatedly read out of the storage tube by a raster scanning system for displaying it on the screen of a cathode ray tube, means is provided to assure precise correspondence between the information train given by the computer and the position on the screen of the cathode ray tube designated by a light pen thus producing an interruption signal to the computer.

Growing community of inventors

Saitama, Japan

Yoshihiro Kawata