| 摘要 |
The invention comprises a three-step switching unit, comprising a number of incoming group related conductors, every group connected to a first switching stage, formed as an input circuit, a number of outgoing group related conductors, every group connected to a second switching stage, formed as an output circuit and a third switching stage. A control unit coacts with said switching stages in order to connect one of said incoming conductors with a selected outgoing conductor by means of a connecting path, pointed out through said between related third switching stage. Each of the outgoing conductors, belonging to said first switching stage coacts with an electro-optical converter. Respective connection between the first switching stage and the third switching stage consists of an optical conductor. The third switching stage is adapted to transfer optical information-carrying signals through said connecting path. The connections between the third switching stage and the second switching stage consists of optical conductors and incoming conductors, belonging to said second switching stage, are pre-connected by an opto-electrical converter.
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