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Normal, Primary Failed, Secondary Failed, Both Fibres Failed, Unit Failed, Master Failed |
Although the Ikon DAI and the SID/JNR fault monitoring systems use different comunication protocols and data speeds, their fault tolerant behaviour is similar, they must use different fibre loops. Both system rely on dual fibre loops connected in opposite directions.
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Normal operation |
In normal operation the "master" unit will transmit identical messages on both fibres. Each slave unit will re-transmit primary messages on its primary fibre output and secondary messages on it's secondary output. Thus the message is passed from unit to unit and finally back to the master.
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Primary Fibre Failed Operation |
If a primary fibre is damaged (e.g. between Slaves 3 and 4 as shown below). The unit beyond the break (4) will start re-transmitting messages received on its secondary fibre input on both of its fibre outputs thus ensuring that all units can still comunicate with the master. As soon as the fault is rectified all units will return to normal operation.
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Secondary Fibre Failed Operation |
If a secondary fibre is damaged (e.g. between Slaves 3 and 4 as shown below). The unit beyond the break (3) will start re-transmitting messages received on its primary fibre input on both of its fibre outputs thus ensuring that all units can still comunicate with the master. As soon as the fault is rectified all units will return to normal operation.
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Both Fibres Failed Operation |
If both fibres are damaged (e.g. between Slaves 3 and 4 as shown below). Each unit beyond the break will start to transmit the data received on the working fibre input on both of its fibre outputs. In the diagram below Slave 4 will return secondary data via the primary fibre and Slave and Slave 3 Primary data via the secondary. As soon as the fault is rectified all units will return to normal operation.
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Unit Failed Operation |
Should a slave unit fail (Slave 3 in the diagram below) the slaves either side of the failed unit will start re-transmitting messages on both fibres as in the case of both fibres failing.
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Master Failed |
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Both the Ikon DAI and fault monitoring system can operate with dual master units. In nomal operation the primary master unit controls the fibre system, the secodary master will operate in the same manner as a normal slave unit. If the primary master fails the secondary master will take control of the fibres. The slave units either side of the primary master will start to re-transmitting data on both of their fibre outputs, as shown below.
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