Cselt-centro Studi E Laboratori Telecomunicazioni S.p.a.

S.i.p. Societa' Italiana Per L'esercizio Telefonico P.a.

Ernesto Viale

Marco Gandini

Giorgio Fioretto

The unit is capable of synchronizing an incoming PCM frame with a PCM frame to be presented at the output, to ensure the sequencing of the channels belonging to a wide-band information flow. The flow can consist of a coded video-signal coming from a video-conference room. The synchronization is accomplished by suitable writing and reading operations effected in a random access memory (RAM) apt to store the information contents of two PCM frames. FIG. 2 is the most significant.

PCM-frame synchronizing unit

A digitally operating telephone exchange, especially one serving an area of low subscriber density, comprises a multiplicity of control units of substantially identical structure programmed to carry out different functions in the establishment and termination of communication among associated subscriber stations. The several control units communicate with one another, and with the subscriber stations, through a common PCM coupling network with the aid of an access unit also having a similar structure. One control unit dialogues with a higher-ranking central office for communication with subscriber stations outside the area served by the exchange.

Automatic digital telephone exchange

A microprocessor associated with a PCM telecommunication network dialogues with remote data-handling components such as other microprocessors through message-interchange circuitry which includes a read/write memory having storage areas individually allocated to several PCM channels, one storage area serving to receive incoming messages destined for the local microprocessor while the remaining storage areas serve for the transmission of outgoing messages intended for respective remote components. A control unit, timed by signals from a synchronization extractor coupled to the network, communicates with the memory to detect state words written by the microprocessor into the memory to indicate the loaded or vacant condition of its storage areas. When the words of an outgoing message are asynchronously written by the local microprocessor into respective cells of a selected transmitting area, a corresponding state word causes the control unit to read out the message words synchronously to the network in the assigned time slot of consecutive PCM frames. Conversely, the words of an incoming message synchronously written into respective cells of the receiving area by the control unit, responding to the arrival of a distinctive start code, are asynchronously read out to the local microprocessor in response to a request signal from the latter.

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Turin, Italy

Ernesto Viale