These are some pics of some old DMC PDH kit recovered from a building stripout (Baskerville House in Birmingham). The kit is made my 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