The department will install Siemens HiPath 4000 Real-time IP system and the Siemens ProCenter 5.1 Contact Centre solution which includes more than 1,400 OptiPoint 500 handsets.
Siemens general manager David Healy said the three-month rollout allows DOFA to protect its existing investment as the solution allows IP and traditional TDM networks to coexist.
"And because the secure core architecture is separate from the user interfaces, security against attacks is at the highest possible level, ensuring system integrity," he added.
Commander business development manager Mike Doering said the easy migration path to new technology allowed Siemens to win the competitive bid.
"We listened very carefully to what DOFA wanted from its new communications network. We are setting the foundation for DOFA to future-proof their network," Doering said.
The HiPath 4000 connects the central location to the other three offices over a fiber optic cable via a wide area network IP link.
Because employees work across all four sites, Doering said flexibility was a key consideration and this included allowing users to connect over IP networks or a traditional circuit-switched system.
He said up to 100,000 IP or TDM users can connect at any given time.
This is in addition to built-in redundancy which guarantees 100 percent uptime from the IP network to a public telephone network (PSTN) as well as the capacity to link a wide range of applications.