I was involved in three failures/isolations, two with TXE4, one with System X.
IIRC, one of the TXE4 failures was a cascade effect (Pulse genny and something else).
I was in the exchange at the time as we saw the affected systems going offline one by one.
The other was two failures which combined and caused the exchange to isolate, the chances of that are very remote.
I was in the another exchange (close by) at the time, we got called over to help get it online again.
The system X failure caused all the remote concentrators to be isolated from each other, I dont recall what caused that.
I was in one of the remote exchanges at the time, you could call other lines locally, but not any other exchanges.
None were fun at the time, but no one got their foil hats out.
