Optus is relying more heavily on automated systems to monitor Triple Zero calls state by state around the clock as the telecommunications group scrambles to improve its mobile networks three weeks after a fatal outage.

The Singaporean-owned company has previously blamed human error for its September 18 Triple Zero outage linked with three deaths. It has also said “there were no alarms to alert us” and “call volumes at a national level did not raise any red flags” when more than 600 emergency calls in four states initially failed to get through.