A growing number of households are ditching fixed phones in favour of mobiles, but that's leaving callers with a problem: which mobile to dial if they want to reach any member of the household free to answer the phone. Swedish mobile operator 3 has a solution: a service that allows a family to be reached on all their mobile phones using one number, which can be either their old fixed line number or a new one on the mobile network.

The service is called 3Hemnummer Familj (3Home Number Family) and can be configured in three ways. The first option is for calls to the family number to ring the mobile phones of all family members at the same time: the first person to pick up takes the call. The second is that calls to the family number are directed to each family members in turn, in a preset order. The last option is that the caller hears a recorded message inviting them to choose who to get connected: dial one for Francis, two for Eleanor, three for Sofia and so on.

The service can handle up to nine users, and costs 69 Swedish kronor (£6.50) per month. The caller pays the same rates as if the call had been made to a fixed phone, according to 3 Sweden.

The network operator developed 3Hemnummer Familj in-house, because that turned out to be the most cost effective option, according to deputy CEO Nicholas Högberg.

Last year, 14 percent of Swedish households only used mobile phones, according to a survey done by PTS, the local telecommunications regulator. That compares to 10 percent in 2008, the survey said. By making the options for families that get rid of their fixed line more flexible, 3 Sweden hopes to convince more families to do so, and to sign up for its services, according to Högberg.

Previously, 3 Sweden had offered individuals the option to get rid of their fixed phone and connect all calls to their old fixed line phone number to a single mobile phone. So far, Sweden is the only country where 3 offers 3Hemnummer Familj, but the operator also has a presence in nine other countries, including Austria, Italy and the UK.