Triple Zero Victoria's computer-aided dispatch system was plunged into darkness at 12.30am on Wednesday.
Emergency Services Minister Vicki Ward confirmed the system was not completely back online until 4am after a 90-minute power outage.
The digital outage forced call-takers to rely on pen and paper to dispatch ambulances, police and fire calls but all were connected.
"We're still investigating this but ... all calls were responded to," Ms Ward told reporters at parliament.
It comes after an outage for Optus customers prevented hundreds of triple-zero calls from connecting in South Australia, the Northern Territory, Western Australia and some parts of NSW.
Three deaths have been linked to the bungle on September 18 when a routine firewall upgrade knocked out emergency calls for more than 12 hours.
Victorian authorities are investigating the cause of the power outage that caused the digital shutdown and why a back-up power supply didn't fire.
"It's never happened before," Ms Ward said.
Triple Zero Victoria, formerly known as the Emergency Services Telecommunication Authority, came under fire during the COVID-19 pandemic after 33 Victorians died as triple zero call answering times blew out.
Hexagon and Fujitsu were handed a $253 million contract in 2024 to update the computer-aided dispatch system following a 2022 review by former police chief commissioner Graham Ashton.
Mr Ashton recommended the system be overhauled, declaring it would not meet the future needs of staff, emergency service agencies and the community.
Opposition emergency services spokesman Danny O'Brien said the state Labor government needed to be clear on when the next-generation system would be up and running.
"This has been happening over the years time and time again," the Nationals leader said.
"It is a concern that people might not be able to get through or calls are delayed because we're having to rely on pencil and paper.
"In the modern age, that's just not good enough."
Victorian triple zero operators were forced onto pen and paper in a similar incident in November after the dispatch system crashed for two hours.
Ms Ward conceded the move to manual dispatch "can be slower" but said it remained a "really quick system".
"Around the world people do rely on manual systems when something is not working as it should," she said.
"So I think that it would be very risky and, in fact, quite reckless to not have a fallback system in place that can be relied on."
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