TOKEN RING FIBER EXTENDERS
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3.1.6
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Main Ring (RI/RO) Operati
The IEEE standard for Token Ring does not define a phantom (intelligent) method of
operation for automatic loopback. As an intelligent mode is desirable in the main ring
between Ring In and Ring Out, many manufacturers developed their own proprietary
methods of operation.
The LCL112A-TR uses a system that is compatible with the standard lobe
mechanism defined in the standard; this is enabled/disabled using the ACL
(Automatic Copper Loopback) switch. With ACL set to ON the NODE/CONC switch
determines whether the LCL112A-TR mimics a concentrator or node. With the switch
set to NODE the LCL112A-TR is configured to connect to a node i.e. uses phantom
current like a MAU lobe port. With the switch set to CONC the LCL112A-TR is
configured to connect to a concentrator i.e. uses phantom current like a
PC/station/router device.
Providing the Ring In or Ring Out port that you are connecting to uses phantom current
in this way, i.e. a Ring In port mimics the station and the Ring Out mimics a MAU then
the LCL112A-TR smart (ACL) mode can be selected.
For maximum compatibility the LCL112A-TR should be set to have ACL off. In this
mode the LCL112A-TR operates in accordance with the IEEE specification and
interoperability is assured.
Note: This requires that the attached MAUs also have their smart RI/RO operation
disabled. This does not apply to 802.5c stations which do not use the phantom current
mechanisms. Examples of 802.5c devices are IBM 8230 CAUs, Madge 8260 CAUs,
RI/RO ports etc.
Summary
For Trunk Operation
For maximum compatibility set ACL OFF, Trunk Mode and disable any proprietary
phantom band smart RI/RO operation on the MAUs.
If the MAUs use phantom current that is compatible with Black Box’s LT4000A
phantom mechanism:
For Ring In connections set
ACL ON
Trunk Mode
Node Mode
For Ring Out connections set
ACL ON
Trunk Mode
Concentrator Mode
