Societa Italiana Telecomunicazioni Siemens S.p.a.

Italtel Societa Italiana

Cselt-centro Studi E Laboratori

Italtel Societa Italiana Telecomunicazioni

Amilcare Bovo

Luigi Canato

Piero Belforte

Bruno Bostica

Luciano Pilati

Giuseppe Valbonesi

Luigi Musumeci

Giampaolo Gubertini

Giuseppe Valsecchi

Convertible switched telephone exchange

A switching unit for the selective transfer of bytes concurrently arriving in successive time slots over eight incoming signal paths to as many outgoing signal paths with intervening temporal and/or spatial transposition comprises a byte memory, loaded by way of a series/parallel converter and read out by way of a parallel/series converter, under the control of a routing memory dialoguing via a logic network with a microprocessor. The latter, through instructions sent to the logic network, may command the blocking of the readout from the byte memory onto an outgoing path during a given time slot, the insertion of a particular byte into such a time slot, or the transfer of selected bytes from either memory to the microprocessor itself. In particular, bytes from the first time slots of PCM frames arriving over selected signal paths can be so extracted from diagnostic purposes.

Switching unit for the transfer of digitized signals in PCM system

A network for selectively switching channels from n incoming PCM links to as many outgoing PCM links comprises two sections of a receiving-side stage with n input terminals each, connected in parallel to respective incoming links, and with m output terminals working into an intermediate stage with 2m input terminals and as many output terminals. The latter are connected to respective input terminals of two sections of a transmitting-side stage with n output terminals each; homologous output terminals of the two transmitting-side sections are alternatively connectable to respective channels of n outgoing PCM links by means of multiplexers which are switched by a logic unit under the control of a processor also detecting possible malfunctions in any section. Each stage consists of a multiplicity of temporal or spatial switching matrices. With m lying between n/2 and n, and with all matrices operating normally, the logic unit routes about half the incoming channels through each receiving-side section and each transmitting-side section; the matrices of the intermediate stage provide a plurality of alternate paths between any receiving-side matrix and any transmitting-side matrix. When a receiving-side or transmitting side matrix fails, the routes established therethrough are transferred to its counterpart in the other section of the respective stage; failure of an intermediate matrix results in a redistribution of its routes through the remaining matrices of this stage.

PCM Switching network with surplus capacity

A coupling network at the junction of several multichannel TDM/PCM links comprises a pair of switching networks each including a set of input group units receiving incoming messages from respective PCM links, a set of output group units transmitting outgoing messages to respective PCM links, and a switching matrix interconnecting the two sets of group units. The bits of a code word representing an incoming message sample, arriving at a line unit individually associated with the respective PCM channel, are delivered to the corresponding input group unit during a receiving period, are read out during a transfer interval via the switching matrix to the output group unit for which they are intended, and are thence fed to the proper line unit during a transmitting period. The two switching networks are identical and have their input and output group units connected to all the line units; a processor, controlling the establishment of interchannel connections through the switching matrix of either of these networks, designates one of them as a master and the other as a slave for standby purposes. A coordinating unit, connected to the output group units of both switching networks (or of corresponding subdivisions thereof), checks on the correlation of their operations and transmits error signals to the processor in the absence of such correlation; this coordinating unit also controls, in response to instructions from the processor, possible changeover from one switching network to the other in the event of a malfunction.

Coupling network for time-division telecommunication system

A telephone exchange linked via PCM channels with subscribers engaged in a conference call includes switching circuits for transmitting to each participating subscriber, during an assigned time slot, the albegraic sum of the digitized voice-current samples from all the other participants. The digitized samples are logarithmically coded, each code consisting of a polarity bit, three range bits and four quantum bits; in order to facilitate correct addition or subtraction of the quantum bits of two codes to be summed (unless these codes signify the two lowest-ranking ranges), according to whether their sign bits are identical or different, the quantum bits of a lower-ranking code are shifted in a register toward less significant bit positions in which they would have their original numerical weight when prefaced by the range bits of the higher-ranking code. The range bits are not summed but only those of the higher-ranking code are preserved, their numerical value being incremented by one in the case of addition but left unchanged or decremented by one (if a negative carry is present) in the case of subtraction. If the difference in rank exceeds the number of quantum bits, i.e. four, the lower-ranking code is ignored.

Method of and system for handling conference calls in digital telephone

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Milan, Italy

Amilcare Bovo