It’s a sort of irony that VoIP plays such as Skype and Viber end up surviving on call termination revenue - that’s to say that without the switched telephony world that they’re trying to replace they’d have to move quickly to a new revenue model - maybe one involving a couple of dollars a year like WhatsApp’s.

Skype, now owned by Microsoft, has long made its money on its Skype ‘In’ and ‘Out’ interconnction services. Incoming calls to Skype users from the switched network have to pay Skype a termination fee, Skype users’ calls to the switched network also involve a fee which Skype skims to give itself a margin. Happy days.

Viber is Skype-like, but born and bred on the mobile handset which seems to have made it a popular solution for smartphone users. Up to now it has followed the usual Internet start-up course of making calls free - all between Viber users of course, across both WiFi and 3G. And it didn’t hurt its cause by providing free Viber to switched network calling in the aftermath of the Philipines Typhoon last month.

Now Viber, which has quietly built up a ‘registered’ user base of more than 200 million, has followed the Skype approach with its own ‘Viber Out’ with per minute prices it claims are significantly lower than Skype’s. Price being perhaps the main reason users go to VoIP for International calls, it will be interesting to see how many Viber users (and indeed Skype users) start making use of Viber Out.

Viber’s service requires some client software and is available on Android and iOS as well as on the desktop. Windows Phone will be rolled out to later next year