Interconnected smoke alarms are wired (or wirelessly linked) so that if one alarm detects smoke, every alarm in the property sounds at once, not just the one nearest the fire.
In a larger home, or one with bedrooms on a different level or wing to the kitchen or living areas, a fire can generate enough smoke to trigger one alarm long before it reaches another. Interconnected alarms mean everyone in the home is alerted immediately, wherever the fire starts.
Properties built after 1 August 1997 in Victoria are generally required to have hardwired smoke alarms with battery backup, meeting Australian Standard AS 3786. Interconnection requirements can depend on the property type and when it was built, so it's worth having a licensed electrician confirm what applies to your specific home.
Older homes with standalone battery alarms can usually be upgraded to hardwired, interconnected alarms without major disruption, and it's a common job alongside other electrical work like a switchboard upgrade.