Datasheet
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Chapter 1
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Personal Computer System Components
FIGURE 1.52 A FireWire (IEEE 1394) alpha cable
Because the FireWire specification was conceived to allow peripherals to be networked
together in much the same fashion as intelligent hosts are networked together in LANs
and WANs, a quick introduction to the concept of networking is in order; see Chapter 10
for more detail on networking concepts. A topology can be thought of as the layout of the
nodes that make up the endpoints and connecting devices of the network. One of the most
popular topologies today is the star topology, which uses a central concentrating device
that is cabled directly to the endpoints. A tree structure is formed when these concentrating
devices are interconnected to one another, each attached to their own set of endpoints. One
or few concentrators appear at the first tier of the tree, sort of like the “root system” of the
tree. These root devices are expected to carry more traffic than other concentrators because
of their position in the hierarchy. In subsequent tiers, other concentrators branch off from
the root and each other to complete the tree analogy.
The 1995 IEEE 1394 specification that is equivalent to FireWire 400 allows 1,023 buses,
each supporting 63 devices, to be bridged together. This networkable architecture supports
over 64,000 interconnected devices that can communicate directly with one another instead
of communicating through a host computer the way USB is required to do. Star and tree
topologies can be formed, as long as no two devices are separated by more than 16 hops. A
hop can be thought of as a link between any two end devices, repeaters, or bridges, result-
ing in a total maximum distance between devices of 72 meters. Through an internal hub, a
single end device can use two IEEE 1394 ports to connect to two different devices, creating
a daisy-chained pathway that allows the other two devices to communicate with one another
as well. The device in the middle affords a physical pathway between the other two devices
but is not otherwise involved in their communication with one another.
RCA
The RCA cable is simple. There are two connectors, usually male, one on each end of the
cable. The male connector connects to the female connector on the equipment. Figure 1.53
shows an example of an RCA cable. An RCA male-to-RCA female connector is also avail-
able; it’s used to extend the reach of audio or video signals.
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