Omnitron Systems Technology FlexCenter 10 - Manual (Page 6)

6 Omnitron Systems Technology, Inc.
INVENTORY
Review content; the following items should be included:
(1) FlexCenter 10 unit.
(1) Power cord.
(1) User’s Manual (this document).
In rack-mounted versions (models 4100 and 4102), the rack mounting hardware may
be an integral part of the FlexCenter’s chassis or it may be included separately:
(1) Mounting ears kit.
Please note any missing items or discrepancies and report them immediately.
INSTALLATION
Cabling and Power-Up
a. Plug the power cord into the FlexCenter10 and the other side to the appropriate AC
wall outlet. The unit power light should turn ON.
b. Plug any Ethernet 10Base-T workstations into the RJ45 connectors. The corre-
sponding Link LED should turn ON.
c. Connect port 1 to a workstation or another hub. When connecting to a workstation
set the Cross-Over switch to its left (Straight) position (factory setting). When
connecting to another hub set the switch to the right (Crossed) position. When the
device at the far end has become active, the port 1 Link LED should come ON.
d. Connect any fiber uplink cables to a fiber workstation, converter or another fiber hub.
Connect the Transmit (Tx) fiber of the FlexCenter to a Receive (Rx) fiber on the
connected device. Connect the Receive (Rx) fiber of the FlexCenter to a transmit
(Tx) fiber on the connected device.
e. Connect any coax uplink cables. When connecting in the middle of a coax cable,
use a “T” connector and set the Termination switch to the right (Termination Out)
position (factory setting). When connecting the FlexCenter at the end of the coax
line, connect the cable directly to the BNC connector and set the Termination switch
to the left (Termination In) position.
Omnitron Systems Technology, Inc. 7
APPLICATIONS
The 5-4-3 Collision Rule
Collisions are an inherent part of Ethernet. Since a sending station may transmit at any time,
its transmission may collide with transmissions from other stations. When a collision is
detected, the sending station backs off, waits awhile and attempts to retransmit again. This
retransmission process is very efficient when performed by hardware. In a large network, if
the delay between two stations is too long, a collision may occur without the sending station's
hardware detecting it Typically, a software function detects the loss of the sent data and
initiates a retransmission process. This retransmission process is very inefficient when
performed by software. The 5-4-3 collision rule was defined by the IEEE 802.3 standard as a
set of criteria that when followed, will ensure the detection of collisions by hardware. The
following paragraphs summarizes the main criteria points.
The main criterion dictates that two stations (DTEs) should not be separated by more than 5
segments and 4 repeaters. When in the maximum configuration the following restrictions
apply: (a) No more than 3 of the segments should be of shared (e.g. coax) type. (b) No fiber
segment should exceed 500 m.
When two stations are separated by 4 segments and 3 repeaters the following restrictions
apply: (a) Inter-repeater fiber segments should not exceed 1000 m. (b) Station to repeater
segments should not exceed 400 m. There are no restrictions on using shared segments.
The 5-4-3 rule is an approximation. In large networks, or when specific distances are
required, the reader is encouraged to use the IEEE 802.3 detailed calculation guidelines
(not described here) or consult Omnitron's application engineering staff to assist in
proper network design.
Application 1. Small workgroup
This application depicts a basic 10Base-T two-hub configuration. The hubs are
connected via a straight-through UTP patch cable with one hub selecting the "crossed
uplink" switch position. The 5-4-3 rule is met since only 3 segments, 2 repeaters and
0 shared media segments are used (3-2-0).