GarrettCom DS8016 - Manual (Page 28)

Magnum DS8016 Dual-Speed Stackable Hubs Installation and User Guide (07/06)
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where 111 is the BT delay for
100m of Category 5 cable (1.112
BT/m* 100m), 80 is the BT delay
for each Magnum DS8016 , 100 is
the BT delay for the TX DTE pair,
and a safety margin of 2 was used.
Figu
re 3.2.3a: Two cascaded Magnum DS8016 hubs
100 m Cat. 5 cables
to user devices
100 m Cat. 5 cables
to user devices
Cat. 5 cable for
cascading
100 COL 10
COL 100 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 X LK/RX PORT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 PWR BR Bl ack Box Rackmount Dual Speed Hub
100 COL 10
COL 100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 X 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 LK/RX
POR T PWR BR Black Box Rackmount Dual Speed Hub
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 DS8016 s. 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 DS8016 s (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 3.2.3b, 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 DS8016 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.
100 m
to us
Cat. 5 cables
er devices
100 m Cat. 5 cables
to user devices
Cat. 5 cable for
cascading
100 COL 10
COL 100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 X LK/RX PORT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 PWR BR Bl ack Box Rackmount Dual Speed Hub
100 COL 10
COL 100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 X
13 14 15 16 LK/RX POR T 1 2 3 4 5 6 7 8 9 10 11 12 PWR BR Bl ack Box Rackmount Dual Speed Hub
Figure 3.2.3b: Multiple
cascaded Magnum
DS8016 hubs
Note that the
cascading of multiple
Magnum DS8016 hubs is a
capability beyond what