Apple's Australian specifications page for both the iPhone 5s and the iPhone 5c confirms both devices will support the 1800MHz FDD-LTE network (band 3), and the 2300MHz TD-LTE network (band 40) used in Australia.
The iPhone 5c variant for Australia will be the A1529 model, while the iPhone 5s is the A1530 device. Both new iPhones come in five seperate models each in order to support various global mobile networks in different markets.
Optus is currently the only telco in Australia to offer both TDD-LTE (time-division duplex) and FDD-LTE (frequency-division duplex) 4G networks, marketed as its "dual band" network.
However, Optus' TDD-LTE on the 2300MHz network band is currently only available in selected parts of Canberra. The telco says the TDD-LTE network will be rolled out across selected Australian metropolitan centres over the next 12 months.
The 2300MHz TDD network uses the entire available frequency for both downloads and uploads, whereas the existing 1800MHz FDD network has dedicated slots for uploads and downloads.
As they support both FDD and TDD 4G networks, the new iPhone 5s and iPhone 5c dual-mode devices simply switch to whichever Optus 4G network is available.
While dual-mode 4G smartphones are relatively new, Apple was beaten to the milestone by Samsung. Optus revealed last month that it would launch dual-mode 4G versions of the Samsung Galaxy S4 and Samsung Galaxy S4 Mini, both currently on sale.
At the time, Samsung said the Galaxy phones were the world's-first TDD-LTE (time-division duplex) and FDD-LTE (frequency-division duplex) devices.
Before announcing the new iPhone models and launching the dual-band Galaxy smartphones, Optus only had a dual-mode Wi-Fi hotspot and a mobile broadband USB dongle (Canberra only) available to customers.