Fujitsu Corporation

Nippon Telegraph and Telephone Corporation

Sony Corporation

Nippon Telegraph and Telephone Public Corporation

Ikuo Taniguchi

Satoshi Ikeuchi

Koichi Nishimura

Satoru Maeda

Kenji Narita

Kenji Yoshimoto

Fumihiro Ikawa

Masumi Kurokawa

Yoshihiro Hanamoto

Koichi Katagiri

Kenichi Hashimoto

An asynchronous transfer mode (ATM) cross-connect unit is used in an ATM communication system which includes at least two communication stations which may be coupled via a plurality of ATM cross-connect units. The ATM cross-connect unit includes an abnormality detector for outputting a detection signal when an abnormality is detected in a first input signal path, a synchronization error detector for outputting a detection signal when a synchronization error is detected in a signal received via the first input signal path, an alarm indication signal cell generator for generating an alarm indication signal cell when the detection signal is received, an alarm indication signal cell detector for outputting an alarm indication signal cell when an alarm indication signal cell is received, a remote alarm transfer cell generator for generating a remote alarm transfer cell, a path setting table in which an output signal path is set with respect to each input signal path and a remote alarm transfer path for transferring the remote alarm transfer cell to a remote communication station is set, and a control part for transferring the remote alarm transfer cell to the remote communication station via the first output signal path according to the remote alarm transfer path set in the path setting table.

Remote alarm transfer method and system

A switching apparatus for a switched network of the asynchronous transfer mode includes a path inspection control device connected to an input interface board, a switching network, and an output interface board. Cells for path inspection are supplied parallel to the input interface board; routing information is supplied to the switching network; the transmissions of the cells for path inspection are simultaneously switched accordingly; the cells for path inspection are delivered in parallel formation from the output interface board; the cells for path inspection delivered from the output interface board are compared with predetermined comparison data, and the routing information and the cells for path inspection or the comparison data are changed in synchronization with predetermined time signals.

Switching apparatus for switched network of asynchronous transfer mode

A system for monitoring an ATM cross-connecting apparatus by rewriting a VPI conversion table to various values, inputting a test cell, and examining the test cell after the test cell passes through the ATM cross-connecting apparatus. Entries of a VPI conversion table are accompanied by traffic flags indicating whether or not the corresponding entry is occupied for use for user's signals. First, the traffic flags are examined. Each entry not occupied for user's signals can be freely rewritten. Each entry occupied for user's signals is not rewritten. The examination of the test cell is carried out by comparing the test cell output from the ATM cross-connecting apparatus, with a reference cell which is expected from a normal operation of the ATM cross-connecting apparatus. The virtual path identifier converted in the ATM cross-connecting apparatus and contained in the output test cell, is expected corresponding to the above rewriting operations, and is contained in the reference cell.

System for monitoring normality of operation of ATM cross-connecting

A switching trigger detection circuit is comprised of a selection unit, a memory unit, and first and second discrimination units. The memory unit stores switching trigger data of each of the line systems related to various switching trigger information at respective bit locations, and the selection unit sequentially specifies the bit location. The first and second discrimination units generate a fault occurrence signal and a fault recovery signal by watching the bit pattern of the switching trigger data stored in the memory unit. A shift of the bit locations is achieved along a guard time including a plurality of guard numbers, and each scan of the swtiching trigger data corresponds to each guard number. Further, the first and second discrimination units are comprised of logic gates to thereby assure a high speed discrimination.

Switching trigger detection circuit in line switching apparatus

A communication system includes a plurality of stations, a first working line coupling adjacent stations among the plurality of stations, a second working line passing predetermined stations among the plurality of stations without dropping therein, and a protection line provided in common for the first working line and the second working line, a supervisory signal always passing through the protection line. Each of the stations includes an internal circuit for receiving an input transmission signal from the first working line and sending an output transmission signal to the first working line. Each station also includes a switching portion for passing the protection line without dropping in each of the stations in a normal mode and for connecting the protection line to the internal circuit in an alarm mode so that the input transmission signal is received from an upstream side via the protection line instead of the first working line and the supervisory signal which is generated from the output transmission signal is output toward a downstream side via the protection line.

Optical communication system having an improved protection line

A line protection switch equipment (LPSW) in a communication system, having a plurality of two-input and two-output switches connected between lines including a protection line and working lines, the switches being connected in series by a loop line which forms a loop, whereby by switching the switches connected to a faulty working line and to a protection line, the faulty working line is switched to become a protection line, and the former protection line becomes a working line.

Line protection switch equipment

A line protection switching system of improved reliability decreases the time for protection line switching. In order to increase reliability, service signals are sent in parallel via a plurality of transmission lines, using a service bit area of PCM bit frames. The system switches a failed transmission line to a stand by line, at a local station where trouble is detected without waiting for the switching of an opposite station. At the same time, a switching command is sent to the opposite station. If the switching of the opposite station fails, the local station commands a retry of the switching operation. If it again fails, the local station returns the transmission line to the initial state. In addition, a low priority signal is transmitted through the stand by line, so that the total system operates more economically.

Protection switching system for carrier transmission line

A signal generator circuit for a television receiver employed in a videotex or CAPTAIN system comprises a reference signal oscillator for producing a reference signal and a synchronizing signal generator for generating a horizontal synchronization signal synchronized with the reference signal. A frequency divider is responsive to the reference signal for producing a color sub-carrier signal. A phase-locked loop is responsive to the sub-carrier signal and includes a voltage-controlled oscillator. The voltage-controlled oscillator produces an output signal synchronized with the sub-carrier signal and having a series of rising edges. A rising edge of the sub-carrier signal periodically coincides with a rising edge of the signal from the voltage-controlled oscillator. A detector detects a time when a rising edge of the sub-carrier signal coincides with a rising edge of the output signal of the voltage-controlled oscillator, and a clock signal is then generated synchronized with the output signal of the voltage-controlled oscillator and having a series of falling edges. The horizontal synchronization signal generator and the clock signal generator are controlled so as to ensure that the rising edge of the horizontal synchronization signal coincides with a falling edge of the clock signal. This ensures an accurate count of the pulses for determining the horizontal position of a display by the receiver and prevents horizontal jitter in the display.

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Kawasaki, Japan

Ikuo Taniguchi