Information Technology Reference
In-Depth Information
Thinnet (10Base2) Cabling
A newer implementation of Ethernet is the 10Base2
thinnet
standard. This cabling
uses a less expensive cable type that is basically RG-58A/U 50-ohm coax cable.
Thinnet was developed during the early 1980s as a cheaper, easier-to-install version
of traditional Ethernet. Sometimes the names
thin Ethernet
and
cheapernet
are used
to describe 10Base2. Thinnet is also a tapped bus topology. A typical thinnet instal-
lation is shown in Fig. B.3. This cable is specified in the 10Base2 standard of IEEE
802.3.
The main topology difference between thick and thin Ethernet is the disappear-
ance of the discrete transceiver and its associated AUI cable. In thinnet, the trans-
ceiver is an integral part of the network adapter of each workstation or server. The
thinnet coax is simply routed from one workstation or server to another in a daisy-
chain fashion. At each workstation's network adapter, a T connector is used to effec-
tively “tap” the coax. In general, a coax cable runs to each workstation where it is
connected to another coax cable that runs onto the next workstation, in turn, until
all have been connected. At the two ends of the run, a 50 ohm terminator is placed
to minimize reflections of the LAN signal. As with thicknet, removing a terminator
or disconnecting a cable will cause the network to fail.
The connectors that are used with thinnet are called
BNC connectors
(see Fig.
B.4). The cable-end BNC connectors are a male, bayonet-style (push on and twist
to lock) connector, originally used for RF connections.
The BNC-T has two female BNC connectors at the top of the T, which are con-
nected to each incoming cable or a terminator, and one male BNC at the bottom of
the T, for connection to the workstation adapter.
Thinnet is often placed into the walls or simply run along the floor and behind
furniture to connect to workstations. If a wall plate is used, two BNC bulkhead con-
185 m Maximum
0.45 m Minimum
Thinnet cable
50
50
BNC-T
Max. 30 transceiver
nodes per segment
Built-in
transceiver
50-ohm
terminator
(each end)
FIGURE B.3
A typical thinnet 10Base2 installation showing distance limitations.
