We are going on a cruise with our two children and we want to be able to keep in contact with them so we know they are safe. Do walkie-talkies work on a large ship? Gary Eyles, Solihull

Sunday Times travel expert, Richard Green, responds: Yes they do, which means that you can be relaxing in your cabin and at the press of a button, and with an added "Roger" and "Over and out" or two just for fun, hear from Johnny that he's watching sports TV by the games room and from Sarah that she's reading outside the ship's library.

You'll save a fortune on mobile phone roaming charges, and they are very easy to use, but all that steel does present a challenge to radio waves. However, unless one of you is below decks at the bow and the other is low down in the stern, the signals should get through all right.

Crystal Radio Systems (01527 872777) sell the Cobra MT750 or the Motorola T5022, each for under £50. They come with twin batteries, two chargers and belt clips, including delivery. If you need four handsets, just order two sets of the same type. Or try Amherst Enterprises (020 7328 9792), or visit your nearest high street electrical shop.

Walkie-talkies will work anywhere in the world, but many countries have strict rules on their use to avoid official users (like the police and fire brigade) suffering interference from sets being used by members of the public. Using them onboard ship and at sea is fine, as it is on land in most European countries, but for the rest of the world it's safer only to use them while at sea.

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