Bernhard Kuemel wrote in a message to William Hargrave:
 BK> [10baseT Concentrator]
 WH> More or less, yes. Except the hub is lower level than that, and 
 WH> most hubs simply work on an electrical basis, and don't 
 WH> specificially route packets.
 BK> So it works as a multiple port repeater?
Yes.
 BK> An input is sent to every other line and collisions are just as 
 BK> possible as with 10Base2?
Yes, although switching hubs can be used at much greater cost.
 BK> How far can such a network be? How long a single cable and how 
 BK> long can a chain of repeaters be?
Each node is permitted to be as much as 100 m from the concentrator. 
Concentrators may be connected to each other, again at most 100 m apart 
(unless an intermediate repeater is used).  The general Ethernet rule that 
there cannot be more than three repeaters between any two nodes applies here.
 BK> How many ports do such concentrators have? 8?
Concentrators are available as small as 4 ports and as large as 32 ports.  
All concentrators can be "cascaded," either with a special port or a 
crossover cable, but this counts as introuducing another repeater.  Some 
concentrators can be "stacked," which does not count as introducing another 
repeater.
 BK> How much do they cost and how much the cables?
In the U.S., we see small 4-port or 5-port concentrators for about US$50.  A 
decent 16-port concentrator would cost about US$200.  More expensive options 
can be obtained, including stackability, remote SNMP management, and 
eventually store-and-forward switching, running the price up to US$2000.
Category 5 UTP cabling costs between US$0.30 per meter and US$1.50 per meter, 
depending upon whether the cable jacket is fire-safe for use in plenum 
spaces, whether the conductors are solid or stranded, and the degree to which 
the cable is rated in excess of the minimum bandwidth requirements.
 
-- Mike
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