These are some pics of some old DMC PDH kit recovered from a building stripout (Baskerville House in Birmingham). The kit is made by DMC (Digital Microwave Corporation). 
It seems to consist of four 2MB/s tribs multiplexed to 8MB/s and then four of the 8Mb/s multiplexed to create the 34MB/s signal which leaves the device on single mode fibre.
See also Digital Microwave 4x2Mb/s to 8MB/s multiplexer
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