Abstract: In a network of communication rings (R1 . . . R7, BB) interconnected by bridges (B1 . . . B4), access to each ring is regulated by a circulating token which is normally issued at irregular intervals depending on occurrence and length of messages. To enable communication of messages which have to be transmitted synchronously, i.e., at regular intervals, each ring has a synchronous bandwidth manager SBM which periodically issues a token for only synchronous information. Each SBM is located in a bridge node (13, 15) but only one of them which is located in a particular bridge node (15) is the master SBM from which all other SBM's are synchronized, using a synchronous token and/or special synchronization circuitry in each bridge. This allows a common period in the whole network for handling synchronous information, even if all rings have different bit rates.

Abstract: In a local communication network, stations can be attached via extension lines and individual ports in distribution panels to the main transmission ring (11). Each port has a physical address or local identification key. Means are provided for inserting the local key of a port into a station when it is plugged into the extension lines. Each station comprises units (33, 45) for generating a key demand signal and an idling signal pattern which are transmitted to the port, and a key register (47) for recording the key when it is received. Each port includes a read-only store and timing unit (41) which furnishes the local key in response to the received idling pattern which is converted to a clock signal. A switch (37) in the port is activated by a switch control unit (35) to insert the read-only store and timing unit into a wrap-around loop interconnecting input and output paths of the station.

Abstract: An improved adapter for a programmed control unit arranged to be operated in facilitating I/O operations between one or more I/O devices and a CPU through a channel. The improved adapter includes a local store which store has a hardware register dedicated to store device status and the associated address in connection with test I/O commands. Thus, in accordance with the method of the invention on receiving a status request the improved adapter responds immediately with a response indicating that the information is not immediately available, for example, a busy response. The improved adapter initiates an interrupt to the program control unit to obtain the requested status information, which is then stored in dedicated hardware registers of the local store. On the next subsequent test I/O command to the same address, the improved adapter responds with the status as read from the dedicated hardware register.

Abstract: A line scanning device which operates under the control of a microprocessor connected to a control memory in which a memory location area is assigned to each line is provided for a line adapter in a communication controller for receiving or sending message bits in series from or to terminals connected to the lines using any protocols. It comprises a first store which includes a first and a second memories, an area being assigned to each line in each of the memories which can be read and written in the same time and a second store which includes a single memory in which a storage location area is assigned to each line.

Abstract: The address generating device is provided for a communication line scanning device. The lines are connected to the scanning device through n line interface circuits, n varying in accordance with the network configuration. Each interface circuit can be connected to a various number of lines, for instance one line or k lines in a preferred embodiment, and comprises means for providing to the address generating device, a presence indicating signal indicating that it is plugged and a signal indicating the number of the lines connected thereto. A first logic circuit receives the presence indicating signals as inputs and generates on its outputs the address bits of the last present interface circuit to be scanned. A first counter able to count in binary mode up to n-1 is incremented by an increment pulse provided by a clock on each period assigned to the scanning of a line. This counter outputs the address bits of the successive interface circuits.

Abstract: Adapter interfaces (ADAPT) and line driver interfaces (RDVP and RDVC) are divided into subgroups within a pyramid type of architecture. Each subgroup is provided with independent preselection means for determining the path through the pyramid from the CCU BUS to the adapter to be serviced first.

Abstract: In a ring communication system comprising several stations, access to the ring is granted to one station at a time by a circulating token indication. A method is provided guaranteeing a transmission opportunity for synchronous or circuit-switched data in periodic time intervals to authorized stations. A CS monitor station issues a frame header which is marked in a specific bit position to allow only authorized stations to transmit their synchronous data together with a destination address. In a first embodiment, a single frame comprises a plurality of slots each having a free/busy indication, a destination address field and a field for synchronous data, and each authorized station can occupy one such slot. In a second embodiment, a marked frame can be used by only one authorized station for transmitting synchronous data, but a new marked frame header is reissued until all authorized stations around the ring have transmitted synchronous data.

Abstract: A method and apparatus for receiving a data signal modulated by means of a double sideband-quadrature carrier modulation technique in which the received signal is sampled at a rate higher than the signaling rate 1/T, passed through a compensating filter, and applied to a processing system which provides the detected data. The compensating filter is such that the amplitudes of the components at f.sub.1 =f.sub.c -1/2T and f.sub.2 =f.sub.c +1/2T, where f.sub.c is the carrier, are equal. An initializer enables a filter coefficient to be determined during the turn-on time of the receiver. An adjusting device allows this coefficient to be continually adjusted. The invention can be used in data transmission systems whose channel has an asymmetric amplitude-frequency response curve.

Abstract: The method allows voice and data information to be concentrated over a reduced number of telephone lines. It consists mainly in processing each voice signal to extract therefrom a so-called analog base band signal and digitally coded characteristic parameters. Said parameters are then multiplexed with pure data and submitted to a modulation operation. The analog signal resulting from the modulation is then added to the base band before being transmitted over a telephone line.

Abstract: In a variable configuration multiplex transmission method, correct sending of data to their respective addressees (terminals 22, 24, 26 and/or 28) supposes that reception station (34) can determine which is the channel configuration from amongst configurations (A, B, C and/or D) that is active. This invention is adapted to proceed to such a channel determination by multiplexing a predetermined particular character from the active channels, directly transmitting over transmission channel (32) the multiplexed predetermined character burst, receiving (34) the multiplexed character burst, and using the received character burst in order to read a pre-registered table which directly gives out that channel configuration which has active channels.

Abstract: Apparatus and method for providing a transmit hierachy for efficiently managing a communications channel. Stations using a common communications channel are equipped with an apparatus for issuing a plurality of consecutive delay times. If energy is not detected on the channel during one of the consecutive time delays, the station is permitted to transmit. If energy is detected a shorter subsequent time delay is issued and the channel is again monitored. Stations are arranged in a transmit hierachy according to the earliest which have attempted access to the channel.

Abstract: An improved split-band coder reduces signal-processing time, thereby reducing echo delay time and listener confusion. The voice-originated signal to be transmitted over a transmission line is sampled and digitally coded at a relatively high bit rate; the spectrum of said signal is then partitioned into p sub-bands. The sample stream of the signal so-filtered and partitioned into p sub-bands is split into blocks of samples, or portions, of a given time duration. A requantizing device proceeds for each block to the requantizing of the samples in each sub-band by means of requantizing parameters derived from the samples of the preceding sample block, whereas new requantizing parameters are determined and stored with a view to requantizing the following sample block. The requantized samples in the different sub-bands are multiplexed, and transmitted over the transmission line, together with the values of the highest amplitude samples in each sub-band.

Abstract: This improved speech signal Block Coded PCM (BCPCM) system reduces the number of bits allocated to transmitting the scale factor, thereby releasing bits for allocation to coding samples in the associated block of samples. The scale factor (c) is calculated for every 16 millisecond block of samples. However, the scale factor will be transmitted only once per 32 millisecond block if there is no significant difference between the two sequential values. The original speech signal is split into 16 frequency subbands, each subband initials sampled and 12-bit coded, then requantized in BCPCM at dynamically variable bit rates depending on the scale factor transmission rate.

Abstract: The improved multiplexer described herein uses split band encoding across a plurality of input ports to increase the statistical advantage for compression gains but does not require a large number of input ports to achieve its advantage.

Abstract: A method and a system for the retransmission of incorrectly received frames in a transmission system in which information is transmitted in the form of sequentially numbered frames. Each information frame includes a so-called send sequence number, N(S), a bit, R, indicating if this information frame has previously been retransmitted, and an information field containing the information to be transmitted. At the transmitting station, a variable, V(T), whose value indicates the order in which a frame is retransmitted relative to the sequence of frames transmitted for the first time, is associated with each retransmitted frame. At the receiving station, the incoming information frames are checked for errors and the N(S) of frames found to be incorrect is noted.

Abstract: A DTMF telecommunication receiver in which an additional DTMF receiver circuit is provided tuned to a particular pair of tones. Detection of the particular tones opens a switch in the audio output line and eliminates crosstalk in the hybrid circuit making detection of further DTMF tones less likely to error.

Abstract: In a ring communication system comprising several stations, access to the ring is granted to one station at a time by a circulating token indication. A method is provided guaranteeing a transmission opportunity for synchronous or circuit-switched data in periodic time intervals to authorized stations. A CS monitor station issues a frame header which is marked in a specific bit position to allow only authorized stations to transmit their synchronous data together with a distination address. In a first embodiment, a single frame comprises a plurality of slots each having a free/busy indication, a destination address field and a field for synchronous data, and each authorized station can occupy one such slot. In a second embodiment, a marked frame can be used by only one authorized station for transmitting synchronous data, but a new marked frame header is reissued until all authorized stations around the ring have transmitted synchronous data.

Abstract: A method of testing a communication network that comprises a first and a second multiport modem communicating with each other through a transmission channel, each of said modems being provided with a number of input/output interfaces and each of the interfaces on either modem being associated with a corresponding interface on the other modem. In accordance with the method of the present invention, a test request is applied to one of the interfaces on the first multiport modem, which responds thereto by generating a test configuration code identifying that interface. This modem is then caused to assume a so-called test configuration, in which only that interface to which the test request was applied is active, and a test command comprising an indication of the test to be performed and a link level identifier is applied to that interface. If the identifier designates the link level to which the first modem belongs, this modem will control the test specified in the test command.

Abstract: In a ring communication system comprising selectively connectable data stations, each station has connecting circuitry including a phase-locked loop arrangement (111) which is frozen at its current frequency and phase in response to a signal interruption caused by a station insertion or removal operation. Control logic (113) generates a freeze control signal in dependence of the signal energy status on input lines (75). This control signal activates gates (149, 151) and switches (155, 157) to interrupt change control signals of the phase-locked loop circuitry and to keep an oscillator control voltage at a given value. The control logic also provides an auxiliary data signal during the freeze interval which is applied to the ring to keep stations downstream in synchronism. By this method and arrangement, undesired reactions and excursions of the phase-locked loop circuitry in response to a signal energy outage are prevented, and synchronization can be rapidly regained after station insertion or removal.

Abstract: In a communication network comprising block switching nodes interconnected by transmission links, a flow control mechanism is provided in each switching node for regulating the flow of addressed data blocks or messages. A hardware look-ahead mechanism effective within each node tests for each data block received from a link and buffered at an input port, whether it can be accepted at the appropriate output port of the same node for further transmission. A token mechanism effective over links permits maintenance at each output port of a node of an indication whether any data block can be accepted in the input port at the other end of the respective link. By the combined operation of look-ahead mechanisms and token mechanisms the flow of addressed messages in a direction where the transmission path is already filled up is prevented. This has a positive smoothing effect on overall traffic flow where short-time or local overloads occur.