primary digital path/pathway

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Note added at 28 mins (2006-05-10 17:32:25 GMT)
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digital path: The whole of the means of transmitting and receiving a digital signal of specified rate between the two digital distribution frames (or equivalent) at which terminal equipment or digital exchanges will be connected. [T1.206-1988] (source - http://www.atis.org/tg2k/)



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Note added at 2 hrs (2006-05-10 19:07:33 GMT)
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an alternative for a digital path is a digital link (Digital Link (Digital Transmission Link, Digital Path)
The whole of the means of digital transmission of a digital signal of specified rate between two digital distribution frames (or equivalent). A digital link comprises one or more digital sections and may include multiplexing and/or demultiplexing, but not switching. The term may be qualified to indicate the transmission medium used, for example, "digital satellite link". The term always applies to the combination of "go" and "return" directions of transmission, unless stated otherwise. The term "digital path" is sometimes used to describe one or more digital links connected in tandem, especially between equipments at which the signals of the specified rate originate and terminate - http://www.pickaxe.demon.co.uk/surftime/glossary2.htm)

so you could use "primary digital link" (or PDL) as in the example below:

following typical digital links and channels are being leased: primary digital link (PDL) with. transfer rate of 2048 Кb/s, main digital links (MDL) with ...
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