Toshiba TOSDIC-CIE DS Instruction Manual page 31

Appendix
Cable segments and link segments
There are two types of segments as defined in the IEEE802.3 standard: cable segments and link segments.
The differences affect the constraints for expanding transmission lines. This section describes the
differences between these segments.
Cable segment
Consists of a set of coaxial cables whose ends are terminated with characteristic impedance. A
transceiver is attached to this segment to connect a station. This is also called as a coaxial segment.
Link segment
A point-to-point connection cable with repeaters (or transceivers) at both ends. No station is connected.
In the TOSDIC-CIE DS system, this refers to the following three types of segments.
- An optical fiber cable with optical repeaters connected at both ends.
- A coaxial cable with electric repeaters connected at both ends, with no station connected.
- A twisted pair cable that connect a hub and station on 10BASE-T (a hub is a kind of repeater).
Maximum network configuration
The "Constraints for expanding transmission lines" are often summarized and referred to as the "5,4,3 rule".
"5 segments/4 repeaters/3 cable segments"
(Up to 5 segments, 4 repeaters, and 3 cable segments)
Some examples of network configuration under this rule are shown below.
500m
Station
Cable
Segment
TR
Figure 1.1 An Example of Network Configuration with Coaxial Cables Only
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Maximum 2500m
500m
Stations cannot
be connected
Link
Segment
TR TR TR
RP RP
500m 500m
Stations cannot
be connected
Cable Link
Segment Segment
TR TR TR TR
RP
Station
500m
Station
Cable
Segment
TR TR TR
RP