Multiplex communications – Wide area network – Packet switching
Patent
1983-12-23
1986-03-04
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370 55, 370 85, H04J 110, H04J 308, H04J 302, H04Q 1104
Patent
active
045743738
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a digital multiplex device for branching a synchronous time multiplexed digital information stream, and more particularly to such a device comprising three four-wire bidirectional transmission gates provided with receivers and transmitters.
BACKGROUND ART
The development of digitized time division general telephone networks has resulted in a need to apply pulse-code modulated (PCM) information transmission methods to individual networks. In these networks, however, the typical 30-channel frame PCM structure produces structural problems and problems related to the quality of information transmission. If, e.g., it is desirable to branch fewer than 30 channels at some intermediate station of such an individual network, all of the 30 channels must be decoded to voice frequency signals and the branching must be performed by connections of these channels, which carry voice frequency signals. Up to three channelling devices must be provided at the station if the branched channels are to be transmitted to another station in digital form. If the channels must be decoded and coded again in this way at each intermediate station, interchannel crosstalk, changes in signal level, and noise may accumulate to disturb the transmission. Moreover, such a branching is quite expensive because of difficulties in installation and the large quantity of equipment required.
A particular problem in relation to individual networks is that the intermediate stations must be connected to both of the terminal stations. Under these circumstances, providing a single branch is not sufficient; but it must also be possible to use the transmission capacity of the main line thereby liberated to serve the connections between the particular intermediate station and the other terminal station.
It is an object of the present invention to provide a device for resolving the aforementioned problems and for performing the branching completely digital.
SUMMARY OF THE INVENTION
In accordance with the present invention an improved digital multiplex device that is relatively inexpensive and can be made in modular form branches a synchronous time multiplexed digital information stream between first, second and third ports. Each of the ports includes a transmitter and receiver. The device comprises first and second selectively activated phase controlling networks. Each of the networks includes: first and second input terminal means and first and second output terminal means, first and second time division multiplexers, first and second switch means and a phase changer. The first multiplexer is directly connected to the first input terminal means of the respective network. The phase changer has an input directly connected to the second input terminal means of the respective network and an output directly connected to a first input of the second multiplexer of the respective network. The first switch means selectively connects the first input terminal means of the network to the first output terminal means of the respective network or it connects a first output of the second phase changer to the first output means of the respective network. The second switch means selectively connects the second output terminal means to be responsive to an output of the first multiplexer of the respective network or to a second output of the second multiplexer of the respective network. The first input terminal means of the first and second networks are respectively responsive to output signals of the receivers of the first and second ports. The first output terminal means of the first and second networks respectively supply signals to inputs of the transmitters of the first and second ports. The second input terminal means of the second network is connected to the second output terminal means of the first network. The second input terminal means of the first network is connected to an output of the receiver of the third port. The second output terminal means of the second network is connected to an input of the tr
REFERENCES:
patent: 4032893 (1977-06-01), Moran
patent: 4124776 (1978-11-01), Nocker
patent: 4205326 (1980-05-01), Porter et al.
patent: 4370744 (1983-01-01), Hirano et al.
Chin Wellington
Olms Douglas W.
Oy Noki AB
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