HOW DID THE OUTAGE UNFOLD?
* Optus initiates firewall upgrade at 12.30am AEST on September 18
* The upgrade blocked calls for Optus users in South Australia, Western Australia and the Northern Territory
* A customer calls Optus contact centre directly about 9am to complain triple-zero calls are not working
* Telecommunications Industry Ombudsman also refers complaints about failure to Optus
* These calls were not handled "as would be expected", based on early review
* Optus becomes aware of "severity" of issue about 1.30pm after another customer contacts the company directly
* SA Police contact company about 1.50pm to report triple-zero calls not working
* The upgrade is cancelled around that time and service is restored after more than 13 hours
* Optus contacts federal government, and office of Communications Minister Anika Wells, to alert them of outage at 2:45pm
* Telco's initial email said "some customers" in SA and WA were experiencing issues with triple-zero calls
* Optus sends another email seven minutes later, saying services had returned to normal and 10 calls were impacted
* Both emails were sent to an old address which was no longer monitored, the communications department says
WHAT HAS BEEN THE FALLOUT?
* Optus chief executive Stephen Rue reveals on September 19 three deaths were linked to the outage
* About 600 triple-zero calls were "potentially impacted", with some not going through
* Mr Rue apologises and defends the delay in informing governments and the public, saying the telco was focused on welfare checks and determining facts
* Officials confirm three people died because they couldn't get through to emergency services
* A fourth death was also possibly linked to the outage
* Ms Wells on September 20 says the Australian Communications Media Authority will run an independent investigation
* Optus vows to appoint an independent expert to review incident
HOW HAVE POLITICIANS RESPONDED?
* Ms Wells hauls in Mr Rue and other telco executives for a meeting at Parliament House on October 7
* The government introduces tougher triple-zero regulations into parliament later that day, aimed at ensuring any future outages are better managed
* The opposition accuses Labor of not doing enough to prevent the Optus outage and responding too slowly
* Bureaucrats on Wednesday reveal Optus' initial notification was sent to an old email inbox which was no longer monitored
* The email downplayed the issue and didn't mention people had died, officials tell a parliamentary hearing
* Ms Wells tells parliament Optus' advice was "inaccurate" and "misleading"
Australian Associated Press
