Telstra has entered into a court-enforceable undertaking to improve its network after an investigation by the regulator found more than 1,400 Triple Zero calls went unconnected during an outage.
The Australian Communications and Media Authority says Telstra failed to direct 1,433 emergency calls to the operator during a May 4 outage that disrupted service in NSW, Victoria, Western Australia, South Australia and Tasmania.
That contravened a rule that requires providers to ensure Triple Zero calls on their networks are carried to the operator.
The problem started with a fire in an inter-state cable pit and was compounded by software failures.
"Triple Zero is the lifeline for Australians in life-threatening or emergency situations," ACMA chair Nerida O'Loughlin said.
"Community confidence in the emergency call service must be maintained."
The ACMA has accepted a court enforceable undertaking by Telstra to improving the redundancy and diversity of its network, develop new disruption protocols, and to ensure its systems are up to international standards.
"The actions Telstra has already taken, and is undertaking, will help strengthen the emergency call service and minimise the risk of another disruption to this critical service," Ms O'Loughlin said.
A Telstra spokesman said the company took its obligations extremely seriously.
"One failed call to Triple Zero is one too many and we apologise again for what occurred," the spokesman said.