• Question: Say if someone is in England and phones someone in Australia, how can they hear each other through the wireless phone?

    Asked by humzaa to Daniel, Jon, Louise, Sharon, Zoe on 17 Jun 2010 in Categories: .
    • Photo: Zoe Duck

      Zoe Duck answered on 15 Jun 2010:

      The sound is carried by radio waves between the two phones. Each phone is able to convert the signals carried by the radio waves into sound waves so we can understand what is being said. Radio waves travel at the speed of light so the delay is hardly noticable

    • Photo: Jon Copley

      Jon Copley answered on 16 Jun 2010:

      The wireless part of that link is only local, between the people’s phones and nearby “base stations” in each country. At the base station, the telephone call is connected from its mobile signal to the wired telephone network.

      The telephone signal carrying their conversation is then carried around the world, between countries, by a global network of fibre-optic cables. These cables run across the bottom of the oceans as “submarine communications cables”. Here’s a map of some of that cable network:

      The cables are laid and repaired by special ships, and they need regular maintenance because they can often get damaged by fishing trawlers, shark bites, and even the undersea volcanoes that I study.

      Less than 1 percent of all the world’s international telephone calls are carried by satellites – nearly all of them are now carried by this network of cables, even if they start off as mobile phone calls in each country.

      In the past, more international phone calls were carried between countries via satellites (and there used to be a noticeable delay when speaking to someone in Australia, because of all the processing of the signals involved), but they have largely been replaced by the global network of fibre-optic cables (and international phone calls are much clearer as a result). But when I’m working on a ship at sea, we still have to use a satellite to phone people back home on land, because obviously we’re not connected to a cable!

      The submarine communications cables don’t just carry the signals for telephone calls – they also carry the communications signals for the internet. Because the cables run through remote areas of the ocean, where they cannot be easily monitored or protected, some people are now worried that they make a tempting target for terrorist or criminal attack.

      We use the internet (and telephone) to do a lot of business, so knocking out the cables would harm the economy of countries, and cause a lot of chaos and disruption. For example, if you look at that map in the link above, you can see that all the undersea cables for eastern Australia come onto land at one point. If you took out the cables at that link, you’d cripple the international telephone and internet links for most of Australia’s cities. It would cut off your phone conversation with England, even if you were both using mobile phones.

      Fortunately, there aren’t many terrorist or criminal groups that have the technology to operate in the deep sea – yet.

    • Photo: Sharon Sneddon

      Sharon Sneddon answered on 16 Jun 2010:

      To start with, a wireless phone is actually a radio — an extremely sophisticated radio, but a radio nonetheless. The telephone was invented by Alexander Graham Bell in 1876. The phone is able to convert the signals carried by the radio waves into sound waves so we can understand what is being said, no matter how far away, as the radio waves travel fast!

    • Photo: Louise Dash

      Louise Dash answered on 17 Jun 2010:

      The microphone in the phone converts your voice into an electrical signal (and digitizes it, for a modern phone). It’s sent by radio waves from the handset to the basestation plugged into your phone socket. This signal is sent via a wire to your local telephone exchange, which then sends it to a bigger exchange, where it’s sent via a satellite to Australia. The signal’s then sent to a local exchange there, and down to the phone of the person you’re talking to, where the loudspeaker in the handset converts it back to sound.

      All of this takes a bit of time though, which is why there’s a few seconds delay when you’re talking to someone on the other side of the planet!

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