Cabletron Systems 24 User Manual

Automatic Beacon Recovery ProcessPage 1-4wrong ring speed. If a ring speed mismatch is detected, the STH disablesthe port to keep the misconfigured station isolated from the ring andprovides a simple visible LED signal (blinking red at the port’s LED) toindicate to the user that Speed Fault Protection has disabled the port. Theport remains disabled until the ring speed mismatch condition isremoved or resolved.Active CircuitryOn each TCU port, STH hubs provide active circuitry which filters,equalizes, and amplifies all received signals before transmitting them tothe next point on the ring. The result is enhanced signal integrity andextended maximum station lobe cable distances.Daughter Board Upgrade KitBoth the STH-22 and the STH-42 can be upgraded to 24 ports using thefollowing daughter board upgrade kits:• TR-UTP-UGKT for STH-22.• TR-STP-UGKT for STH-42.1.2.3 Automatic Beacon Recovery ProcessTo guard against interruptions in network operations due to beaconingconditions, the STH supports Cabletron Systems’ advanced AutomaticBeacon Recovery Process which automatically partitions problematiclobes from the ring, allowing the rest of the ring to continue operating.(ABRP engages even before the IEEE standard beacon recovery processbegins and is able to treat conditions beyond the scope of the IEEEprocess.) It is the stack’s intelligent hub that actually executes the ABRPalgorithm. The intelligent hub also checks partitioned lobes periodicallyand re-enables them automatically once they have recovered.1.2.4 Support for Passive MAU WorkgroupsWhereas a station signals a TCU to open its interface by sending aphantom current down its lobe cable, a passive Multi-Station Access Unitcan not provide phantom current. A TCU Ring Out port is thereforeconfigured to ignore the absence of phantom current in the connectingcable and to look instead for the presence of data bits to determine linkstatus.