• A 76-minute Optus voice outage affected 190,000 customers and left 46 Triple Zero calls unable to connect
  • Investigators will examine whether emergency calls moved to other mobile networks as intended

The fact

A hardware failure at an Optus exchange in Victoria caused a 76-minute voice outage on 11 September, affecting customers in parts of Victoria, South Australia, Tasmania and the Northern Territory. Optus said about 190,000 customers had two call attempts that did not reach their intended recipient. Forty-six Triple Zero calls were among those affected, with police conducting welfare checks and reporting no adverse outcomes.

Optus replaced the failed hardware and restored service. The Australian government said the incident was deeply concerning and pledged to keep strengthening telecom network resilience.

Mobile emergency calls have a separate fallback mechanism. If a customer's own network is unavailable, a handset can use another available mobile network through emergency camp-on. Since November 2025, Australian rules have also required operators to prevent failed infrastructure from obstructing that process. It is not yet clear how camp-on performed during this outage.

The assessment

Australia already has a fallback for emergency calls: if one mobile network fails, the handset should be able to use another. The harder case is when the failed network is still visible to the phone but cannot complete the call. The network then has to recognise the fault and stop holding the handset on a path that no longer works.

It is not yet clear whether that happened during the Optus outage. Investigators need to establish when Optus detected the failure, whether emergency camp-on was triggered and how long affected callers remained unable to connect.

For BTW readers, the issue is not simply whether another network was available. It is whether callers could reach that network quickly enough. A backup path offers little protection if the phone remains attached to the failed one.

What to watch

Watch for the ACMA and Triple Zero Custodian findings on how many affected calls later connected through another carrier and whether emergency camp-on was triggered. The timing between the hardware failure, network detection, any failover action and final restoration will show whether the main weakness was the failed equipment or how the network responded to it.