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

Cselt- Centro Studi E Laboratori Telecommunicazioni Spa

Mario Bondonno

Piero Belforte

Luciano Pilati

Enzo Garetti

Bruno Bostica

Giancarlo Guaschino

An automatic exchange of a telephone system comprises a PCM switching network with a plurality of cascaded stages for establishing temporal and spatial connections between incoming channels on input lines of the first stage and outgoing channels on output lines of the last stage in response to commands from external controllers dialoguing with internal controllers of the network. Pairs of switching matrices forming part of nonadjacent stages are combined ito modular switching units each provided with its own internal controller. Routing instructions are transmitted from an external controller to a first internal controller which selects a signal path through the matrices of its own switching unit and informs a second internal controller of that selection whereupon the latter extends the path through an adjoining switching unit, and so on until the connection is completed. Each matrix is provided with a data store which is asynchronously loadable from the associated internal controller with a routing instruction to be synchronously forwarded, in a special time slot dedicated to intercontroller dialoguing in a PCM group to which the instruction pertains, to the data store of a coacting matrix in the next stage for asynchronous retransmission to the controller thereof; each data store may be paired with a respective series/parallel converter coupling it to the associated matrix for serially loading that store in any PCM frame with the contents of the dedicated channels of concurrently arriving PCM groups and feeding stored instruction words in parallel to the output lines of the matrix during a predetermined time slot of each frame. The internal controllers also perform diagnostic operations by comparing bytes extracted from an established signal path at locations upstream and downstream of a matrix.

Modular self-routing PCM switching network for distributed-control

A five-stage PCM switching network of an automatic telephone exchange is divided into a set of outer modular units each including a first-stage and a fifth-stage matrix, a set of inner modular units each including a second-stage and a fourth-stage matrix, and a set of central modular units each including a pair of third-stage matrices. Each modular unit is provided with an individual base-level microprocessor controlling the switching of its matrices and the checking of their performance with the aid of ancillary equipment including transceivers sending back outgoing signals and samplers delivering bytes from corresponding time slots at opposite ends of an established signal path to a comparator in the associated microprocessor. Each set is divided into several subsets provided with respective intermediate-level microprocessors which control their base-level microprocessors; a top-level microprocessor, responsive to commands from a central controller, dialogues with the intermediate-level microprocessors for setting up and discontinuing calling connections between incoming PCM lines joined to inputs of the first-stage matrices and outgoing PCM lines joined to outputs of the fifth-stage matrices.

Modular structure for multistage PCM switching network

Growing community of inventors

Borgaro Torinese, Italy

Mario Bondonno