| 摘要 |
A data transmission equipment, known as a primary digital multiplex (PDMX) consists of a bus structure formed by parallel lines on a printed circuit board, with the circuit units (1,2,3,4,5) on printed circuit cards set at right angles to the bus structure. The circuit units include a control unit (1,2) also called a core facilities unit, which acts as an interface to one or more 2Mb/sec. trunks, and so-called tributary units (3,4,5) which give access to subscriber and other outlets. Various networks using one or more such PDMX equipment are described. The signalling and control arrangements for the equipment use a signalling processing unit (2) and a tone processor (6). The signalling processing unit monitors the bus for signals and line conditions and issues signals appropriately. The tone processor functions in a generally similar manner. Note that PDMX is one of STC PLC Trade Marks.
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