GarrettCom 8000X - Manual (Page 33)

Magnum 8000X Mixed-Media Fiber Hubs Installation and User Guide (05/ 02)
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The resulting value tells us that a Category 5 cable with a length of up to 25
meters may be used to cascade the Magnum 8000Xs. Note that this inter-repeater cable
length may be increased by shortening the lengths of the 100m hub-to-user cable
segments.
It is also possible to cascade a group of up to nine Magnum 8000Xs (serving
up to 56 users with full-length 100m cables to each) by using short inter-repeater cable
segments. The following is an example of how to calculate the maximum allowable
cascade cable segment length. An illustration of this example is shown in Figure 3.6.1b,
where the hub-to-user cable lengths are up to 75 meters for Cat 5 twisted pair. The
variable “X”, the maximum hub-to-hub cable delay, is calculated as follows:
PDV = X + ((100) + (80 + 80 + 80 )+ (83 + 83) + 2 ) BT < 512 BT
512 > (X + 508) BT, X < 4 BT
Twisted pair user cable length, TL < (4 BT) / (1.112 m/BT)
TL < 3.6 meters for two hub-to-hub cascading cables
⇒ 2 meters (6 ft.) length max. for each of the cascade segments,
In the above example, 75 is the BT delay for 70m of Category 5 cable (1.112 BT/m), 80
is the bit time delay for each Magnum 8000X front-to-front ports, 100 is the BT delay
for the TX DTE pair in the user
stations, and 2 BT is the safety margin
applied.
Figure 3.6.1b: Multiple cascaded
Magnum 8000X Mixed-Media hubs
Note that the cascading of multiple
Magnum 8000X Mixed-Media hubs is a
capability beyond what industry
standards normally permit, and is different from what competitive 100Mbps Class II
hub products normally allow. This additional cascading level and cable length is due to
the relatively shorter bit time (80 BT actually measured, for front-port-to-port) delay of
the Magnum 8000X vs. the industry standard delay of 92 BT for Class II repeaters. The
installation flexibility and network growth potential is accordingly better with Magnum
8000Xs than with hubs that merely meet the standard. Table 3.6.1c shows maximum
cable lengths for common network configurations using industry standard repeater PDV
numbers. Calculations such as above should be performed using measured PDV data
supplied by the equipment manufacturer in important installations.
2 meter Cat. 5 cable
for cascading All user devices connected
via Cat. 5 twisted pair cable
of up to 75m length.
10100 PWR BRD
ACT COL
Magnum 8000X
Mixed Media Hub
GARRETT 1 R L S R L S R L S R L S R L R L R L R L R L R L R L R L R L R L R L R L
10100 PWR BRD ACT COL
Magnum 8000X
Mixed Media Hub
GARRETT 1 R L S R L S R L S R L S R L R L R L R L R L R L R L R L R L R L R L R L 10100 PWR BRD ACT COL
Magnum 8000X
Mixed Media Hub
GARRETT 1 R L S R L S R L S R L S R L R L R L R L R L R L R L R L R L R L R L R L