Introduction to Data Communications
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45k. CAUs & LAMs

Smart concentrators or Hubs are called CAUs (pronounced cows) in Token Ring. CAU stands for Control Access Unit. It has a CPU built in and the smarts to control and determine when a Node is operating incorrectly. It can determine if the RI or RO main ring is operating properly. CAUs can make decisions on disconnecting nodes or wrapping the Main Ring to the Backup Ring. They are also able to be controlled and programmed from a remote station - SNMP compliant (Simple Network Management Protocol). Nodes can be remotely disconnected from the Ring. CAUs controls LAMs.

A CAU can control up to 4 LAMs (pronounced lambs). LAM stands for Lobe Access Module and LAMs have the Lobe connections. The CAU is connected to the LAMs by a Power Connection and a Data Connection. A LAM has 20 lobe connections. A LAM is an active concentrator.

Active Concentrators

An active concentrator is a concentrator that retimes and regenerates the data signal. It does the job of a repeater. Since it retimes and regenerates the data signal it is not used in Ring Length calculations.

Introduction to Data Communications
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