Cabletron Systems MicroMMAC 24T MICROMMAC- - Manual (Page 12)

INTRODUCTION
1-4
Active TCU Ports
The active TCU ports regenerate, reshape, and filter the incoming signal,
permitting UTP lobe cable lengths of up to
120 meters and STP lobe cable
lengths up to 150 meters at 16 Mbps ring speed. The MicroMMAC-22T
and the MicroMMAC-42T can be upgraded in the field using the Cabletron
UTP and STP 12-port upgrade kits.
Cable Signal Polarity
Differential Manchester encoding is used for each concentrator module
TCU port. This permits passing data regardless of receive link polarity.
NOTE : The MicroMMAC-T is not affected by the reversed polarity
condition. If, however, such a condition is discovered, the segment should
be removed from the network and wired correctly to avoid problems during
future network operations. Refer to Section 3.8 for cable pinouts
specifications
Speed Fault Protection
If a station attempts to insert into a ring port at a different speed from the
one set on the MicroMMAC-T, that port is automatically bypassed to
prevent the ring from beaconing. The Lobe Port Status LED blinks red (for
more information, see Section 5.1, USING LANVIEW LEDs) to indicate
that the port with the speed fault is being bypassed.
Local Management
Local Management provides you with the ability to manage the
MicroMMAC-T and all of its attached segments, including most BRIMs
and the MicroSNAC device. The CR BRIM-W/T and the MicroSNAC
provide their own configuration firmware.
Access Local Management by connecting an actual or emulated Digital
Equipment Corporation VT100™ series terminal to the MicroMMAC-T’s
COM 1 port or the COM 2 port. To view diagnostic test information from
a display terminal, use the COM 2 port.
Token Ring Port Interface Modules (TPIMs)
TPIMs are modular connector cards used for expanding trunk connections
to a range of Token Ring media. TPIMs have embedded repeaters that