Telstra is investigating what caused a national outage that stopped trains, transactions and some Triple Zero calls.

The telco believes a software defect is behind the outage

The widespread outage is affecting mobile calls and data connections, and has even prevented some businesses from processing payments.

The widespread outage is affecting mobile calls and data connections, and has even prevented some businesses from processing payments.

Telstra customers are reporting problems connecting to the internet and making calls this morning. Follow live.

Tech expert Trevor Long discusses Telstra's major network outage affecting customers this morning.

Mobile and internet services are affected as the telco says it is "looking into" the problem.

Trains in Victoria and NSW were brought to a standstill as thousands reported issues with their Telstra network on Wednesday morning.

Follow our live coverage here.

July 8 : An outage hit services of Australia's biggest telecommunications company Telstra on Wednesday, disrupting taxi payment systems and some train services, with the…

Here are the underlying tech connections between a telecommunications network crash and rail service disruptions.

Eftpos terminals have been affected too, with some small businesses switching between payment machines and offering PayID transfers.

Telstra said about 90 per cent of calls were restored by 10am Wednesday. But phones weren’t the only technology impacted.

Carrier restoring mobile services after network used by millions goes down for many users, shutting down regional trains and affecting emergency calls

These outages have exhausted public patience, and promised fixes aren’t being felt yet.

Telstra is working rapidly to bring its mobile network back online, after hundreds of thousands of customers were caught up in a nationwide outage.

Telstra is investigating what caused a national outage that stopped trains, transactions and some Triple Zero calls.

V/Line services have been thrown into chaos after a major Telstra outage affected signalling.

A nationwide Telstra outage cut phone service, halted regional trains and froze card payments across Australia. Telstra blamed a network timing fault.

Telstra’s nationwide outage caused chaos in Victoria on Wednesday, with dozens of Triple Zero calls dropped and thousands of commuters stranded.

The Telstra outage has seen the iconic Ghan ground to a halt.