Sycamore Networks DNX-1U¶
This is a device that apparently was used primarily in the context of (E1 based) back-haul of 2G (GSM/GPRS/EDGE) sites. It has multiple high-bitrate serial ports, E1 lines and Ethernet ports, and is capable of multiplexing between the 64k time slots on each of those E1 lines. So you can use it to "concentrate" signaling and traffic timeslots from multiple (not fully utilized E1 lines into some other E1 lines which then are fully utilized.
The Ethernet/IP traffic can apparently also somehow be encapsulated/transported over E1.