Are they empty cans? Or are they high-tech devices?

Tin "cantenna"

In Peebles Valley, a small rural community in eastern South Africa, they demonstrate how tin cans could link the people of this community with each other, and the wider world.

To prove the point Click visited an Aids clinic where 2,000 patients receive treatment. The clinic has long had a satellite dish to access its online database, but until recently the idea of making contact just over the hill was a different story.

Clinic manager Harry Munnings said: "The biggest problem was the communication between the clinic and the community hospice; the doctors are at the clinic and the nursing team is at the hospice, and if they ever wanted to call the doctors it could get quite complicated."

No landline or mobile signal, and two places several kilometres apart who needed to talk to each other.

Cabling an area like this is too expensive, so some kind of wireless link would seem to make sense.

However, a conventional wi-fi network setup does not have the range. A regular wi-fi aerial ripples the beam out in every direction, which limits how far it can travel. And that is where tin cans combined with antennas come in - the so-called "cantenna".

Stick the antenna inside the can and the can's shape and characteristics focus all the energy of the beam in one direction.

It is astonishing to think a cantenna can push a signal across such a distance, but there are some drawbacks. Over time, they rust, which means they need to be replaced.

More significantly, cantennas need a direct line of sight to each other, or they will not work at all.

That is a problem in this hilly terrain. So the answer is to connect the clinic to the hospice indirectly, using other cantennas dotted around the hills in a so-called mesh network, which seamlessly passes the signal from one point to another.

The benefits are huge. The hospice has got online and is connected directly to the clinic. Nurses use voice-over-internet calls back to the clinic, and they have access to the online database of patients too.

And what is really cool is that everybody else involved whose cantenna links to the network gets on the network too.

This means they get internet access, can send instant messages, e-mails and make net phone calls.