Here is my possibly incorrect understanding.
Starting from the blinky end..
A Smart String is a 12v pixel string of 1 .. 128 RBG nodes, attached to a Smart String Controller (SSC). The core of a SSC is a PIC24 chip and a RS-485 receiver. Output is 12V power and 5v data to a 3 wire TM180x based pixel string. Input is a RJ-45 to Cat 5, with RS-485 on pair 1, and 12 V power on the other 6 conductors (3 power, 3 gnd). It receives Smart String Protocol at 1 Mbps, with 4096 one-byte channels in each packet, as a max of about 30 times/second (4097 bytes/ packet * 30 * 8 bits/byte < 1 Mbps). The SSC is programmed for a start address within those 4096 channels, and a length (3..384 channels for 1..128 RBG nodes).
Upstream of this would be a Hub. A 16 port hub or a 4 port passive hub (?).
The 16 port activehub distributes 12V power from a (potentially large) external power supply to its 16 outputs. It also receives 4096 one byte channels (in the same 1 Mbps RS-485 Pixelnet format) from upstream, and distributes that same packet to its 16 outputs (RJ45 to Cat5 to SSC). The upstream link is also RS485, however it does not need to supply power so all 4 pairs are available for Pixelnet data; the 16 port Hub selects which of the 4 pairs it will receive from. It can pass all 4 pairs downstream to another 16 port hub (daisychaining); the downstream hub could select its input from the same pair (sharing the same or different portions of the same 4096 channels of a pixelnet packet on that pair), or a different pair. With four daisychained 16 port hubs, each selecting a different Cat5 pair, there could potentially be 16384 one byte channels distributed from the same Cat5 cable (via four 1Mbps RS-485 pairs).
A 16 port active hub can directly connect to 16 SSCs, each of which can handle 1..128 pixels. That would mean a maximum of 2048 pixels (6144 one byte channels). In practice it can control at most 1365 independent RGB pixels. Of course, many strings will be shorter than 128, so it's very flexible to have 16 outputs.
The 16 port active hub can also extract 512 bytes (on a 512 byte boundary) from among the 4096 it listens to, and output those as DMX (250 Kbps RS-485 on one pair of Cat5+Rj45 using DMX protocol). Those 512 channels are still available to pixels, if the pixels don't mind having the same data - just as two SSC's could be programmed to extract the same channels or overlapping channels, but would be duplicating channel data.
Upstream of the 16 port active hub there are a couple of choices: the USB pixelnet dongle and the EtherDongle; we'll describe the former first. The same hardware which is used for a LynxUSB to DMX dongle can with different firmware become a USB to pixelnet dongle. It will then output 4096 one byte channels over RS-485 at 1 Mbps on pair 1 of its RJ-45->Cat5 output. The USB input to the dongle goes to your computer (usually directly, tho there exist various USB extenders which may work for you).
If you had only one USB Pixelnet Dongle, it would be sending Pixelnet on only the first pair of wires, and there would be only 4096 downstream channels available for any and all downstream 16 port hubs (all of which would need to be set to listen to the first pair). However, you could use the Lynx Combiner to merge up to 4 USB Pixelnet Dongle outputs onto a single Cat5 cable (one pair from each input would be wired to each of the 4 pairs in the output Cat5). Each additional USB to Pixelnet Dongle merged in this way would add 4096 channels which daisychained 16 port hubs could listen to. So with 4 USB to Pixelnet Dongles going into a Lync Combiner onto a single Cat5 and thence daisychaining at four 16 port hubs (each selecting to listen to a different pair), you could get a total of 16384 channels out to SSCs (for them to extract their programmed set of channels from).
At this point in the description, there are two cable types used in Pixelnet. Both are Cat5 connecting to RJ-45 jacks. There is a data-only cable containing 1-4 pairs of 1 Mbps RS-485 pixelnet from dongles to hubs, and a data+power cable containing 1 pair of 1 Mbps RS-485 pixelnet plus 6 conductors of power from hub to SSC.
The EtherDongle adds another option to this mixture. You might say that it replaces 4 USB Pixelnet dongles and a Lynx Combiner, with a single superdongle which takes Ethernet as its input rather than (four) USB cables. This means that it uses Cat-5 cables and RJ-45 connectors in yet a third way - to carry 10Mbps or 100Mbps ethernet from the computer to the Etherdongle. That could be directly connected (with appropriate crossover able or autoMDX ports) or more often through an ethernet switch or even WiFi network.
The EtherDongle receives 16384 channels over ethernet, and puts them out on a single Cat5 (as four 1 Mbps PixelNet pairs). It will take at least four 16 port active hubs to distribute this to SSCs (each selecting one pair from the Cat5 and thus receiving and distributing 4096 one byte channels).
Cables (all Cat5 or higher using RJ-45 connectors):
Ethernet - up to 100m - 10Mbps or 100Mbps - Computer to Etherdongle
Pixelnet backbone - up to 1000m - 1 to 4 times 1 Mbps - Etherdongle or USB pixelnet dongle to 16 port hub
Pixelnet distribution - up to ? m - 1 Mbps plus power - 16 port hub to SSC
And in addition to this, each 16 port hub can also output one DMX universe on another Cat-5
DMX - up to 1000m - 250Kbps - 16 port hub to DMX devices like Lynx Express
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Is the above correct? I offer it for the Wiki if useful (or I can add it to the wiki with permission). I had to extract the above from MANY forum posts, wiki pages, and downloadable files from each.
I might do a diagram later. I want to confirm that the above is accurate first.
The 4 port passive hub is not included in the above, because I haven't yet located a description of where it fits in... not sure what it does that the Lynx Combiner would not do. I'm sure I just need to read another 100 forum messages, it must be in there somewhere (grin).
