Abstract: Communication controller allowing communication between application programs running in at least one host computer and DTEs attached to a X25 packet switched network and communicating through virtual circuits (VC), the communication being provided through the X25 network and a Systems Network Architecture (SNA) network. The controller includes tables and logic for establishing predetermined SNA sessions between the application programs and the communication controller, and tables and logic for linking at least one virtual circuit on a predetermined SNA session. The controller further includes memory for storing a set of alternate session tables defining, for each of said established predetermined SNA sessions, a prioritized list of alternate backup sessions, logic for detecting the occurrence of one failure on one SNA session, and logic for switching the virtual circuits linked to said session being subject of a failure to one backup session defined in the corresponding alternate session table.

Abstract: A communication controller CCP includes line adapters (104-i) each having a storage which is loaded with a general application program during an initialization phase. The line adapters allow the attachment and the communication of different telecommunication entities, e.g. a LAN, a teleprocessing line etc. . . The CCP is connected by means of a control adapter to a local control terminal (100) which is associated with a storage for storing the different general application programs which are likely to be required by the different line adapters. A storage contains an access key comprising data relative to the types and the number of line adapters of any type which are authorized to be loaded with the general application program stored in the storage controlled by the control terminal. The CCP also has logic for checking whether a loading request received from one adapter complies with the contents of the stored access key in order to prevent the loading of an unauthorized line adapter.

Abstract: A method of operating a communication system which includes a number of host systems each communicating via sessions with other devices over different connections and in which the sessions assigned to a failed connection are suspended for a first and second time period and non-destructively moved to an alternate connection when a unique command is issued by one of the host systems and received by a control unit involved in the failed connection.

Abstract: In a packet switching network, voice packets are made to include an EC field whose contents indicates whether the corresponding packet is eligible for clipping if required in a node queue within the network. Should clipping of a non eligible packet be required, then another bit field would be set in the following packet on same link to limit any possible clipping of successive packets on same link.

Abstract: A method of reconstructing, at the receiving end, digital data defining an encoded voice signal segment lost in transmission between the transmitter and the receiver in a transmission system wherein a low-frequency signal such as a residual baseband signal is derived at the transmitting end from the signal to be encoded and is then distributed among several sub-bands whose sampled contents are quantized separately. The reconstruction method includes a step of analyzing the received signal to detect any missing segment thereof and, as the case may be, to initiate an analysis, within each sub-band, of the segment(s) adjacent to the lost segment, so as to generate a term relating to the period T.sub.(k) of the signal so analyzed and to reconstruct a segment of signal of period T.sub.(k) intended to be substituted for the lost segment. Cyclic redundancy is used to detect errors, and modulo sequence numbering identification is used to detect loss of packet.

Abstract: In a voice transmission network having an echo canceler including a flat delay line in series with an adaptive digital filter, a process is provided for adjusting the flat delay line length, thus enabling limiting the filter length to minimal value. The method is based on intercorrelation operations. It includes first intercorrelating sequences of energy values of blocks or consecutive samples, to derive a rough flat delay estimation therefrom; then intercorrelating sequences of signal samples with one of the sequences being roughly delayed, to derive therefrom an accurate flat delay estimation.

Abstract: This process enables cancelling residual echo signals in a transmission system wherein echo signals are partially cancelled through use of a filter generating an echo replica, and substracting said replica from the signal in the echo path. The process involves measuring energies of incoming and outgoing signals, comparing the ratio of said energies to a predetermined threshold value to generate a flag information, which flag is used to control a switch on the echo path. The threshold is determined, for instance by using the information provided by the echo path impulse response not considered for the generation of the echo replica.

Abstract: A buffer device for a digital transmission network transmitting voice signals, by packets, including so-called purging means for eliminating a number x.sub.(t) of the oldest packets stored in the buffer to prevent saturation thereof. The number of packets received at the input of the buffer within a given time interval is used to address a storage that supplies two pre-stored digital values, namely, x.sub.(t) and L.sub.(t). When the contents of the buffer are equal to L.sub.(t), a number x.sub.(t) of the oldest packets contained in the buffer are dropped.