Softphone maker Cicero Networks has launched a Symbian version of its dual-mode phone software to capitalise on the success of phones like Nokia's E-series against Windows Mobile devices.

The softphone from Dublin-based Cicero offers seamless handover of calls between the mobile network to a voice over IP link on a WiFi connection, and will be available at the end of November for operators to offer converged phone services delivered on handsets such as the Nokia E-series.

"We started on Symbian in 2002, but our early development on series 60 devices hit an intractable roadblock," said Ross Brennan, chief executive officer of Cicero. "the inability for handsets to support full duplex audio. We switched track to the Windows environment, but re-started development of a Symbian client in summer 2005, because of the future release of Nokia E-class handsets."

The Nokia E-series (including the E61 reviewed here) has become an important handset for converged voice, with services like Truphone launched on it.

Cicero uses a As well as the softphone, (which we reviewed in 2005), Cicero's products include a roaming server to support handover between the two networks, part of the company's evolving offering.

A service using Cicero's softphone can make intelligent choices about which network to use, because it loads a new phone dialler onto the handset that takes charge of dialling both cellular and WiFi calls. Services like Truphone, which use the native Nokia dialler, will always involve the user making a decision as to which network to use, he said: "The user doesn't want to change their behaviour in any way," said Brennan. "We do produce user documentation for our phone, but if you have to refer to it, we've gone badly wrong."

The seamless roaming from one network to another is provided by a hand-off server on the operator's network, and does not use the UMA standard. The hand-off server dials a call on the conventional network to take the place of a call carried on WiFi, when necessary. Although Cicero provides these servers, they are built to a standard defined by the 3GPP body, which defines how handover should be done, so eventually clients from one vendor will work with servers from others, he said.

While Symbian is the leading smartphone platform, operators are likely to support both Symbian and Windows devices, and using the same client will make this easier, said Brennan.

Cicero's softphone is currently offered by four operators - Norway's Hello, Italy's Messagenet, Talk Telecom in Ireland, and the roaming enabler Comfone.