There has never been a better time for the traveller to go almost anywhere and still be in touch by means of telecommunications - but be careful, because convenience can come at a price. However, with a little thought and some background knowledge, it is possible to keep costs low - and still get what you want. The first step is to consider what your needs actually are: for instance, are you travelling for business or pleasure? Where are you going? What degree of mobility do you require? Do you just need telephonic communication or do you need both voice and data services, including internet access? Is your use of telecommunications going to be frequent or occasional? Making a decision about the best option for you depends on an adequate assessment of all of these criteria. Moreover, products and services are not necessarily identical in every country and getting a single 'international' solution, usable anywhere, will probably be impossible or extremely difficult.

Voice communications

We tend to forget how amazing it is that you can now make a phone call to anywhere in the world. International direct dial (IDD), enabling effective person-to-person calling, is now available in almost all countries. A minority still require some form of operator connection, but bear in mind that such conditions exist mainly in war zones.

IDD is theoretically available from almost any public payphone, residential phone, mobile phone or hotel phone in the world. However, it's worth bearing in mind that it can be an expensive option, and may not always be available. In a number of countries, such as Japan, for example, international operators are separate from the local ones and require booked, pre-assigned or special access arrangements. Likewise, international payphones in Japan are distinguished from national ones.

Wherever you happen to be, watch out for hotels and other sites that simply bar international access altogether to avoid being caught with large unpaid bills. Outside in the street, using a payphone means you have to work out how to pay. Unless you are flush with foreign currency, the only option is likely to be the use of a card phone (see below).

You should also recognise that many hotels probably make as much profit from telephone calls as they do from renting rooms. Call charges from hotels are likely to be extremely high. Some have begun to reduce tariffs recently, due to the pressure of unfavourable media attention, and the more responsible hotels notify you of the charging structure in advance, but you should always check and, if possible, arrange for people to call you instead. Note that hotels often make high charges for faxes, too, and many charge for inbound faxes.

PTT bureaux exist around the world, especially in countries where telephonic access has, traditionally, been poor. They provide a walk-in service for IDD, fax, and telex services at stipulated IDD rates, on a cash or sometimes credit card basis. Tourist information offices should always know where they are located.

One of your best bets is to use some sort of card phone, of which there are several different types. Prepaid card phones are exactly what their name suggests: these are payphones for which you must buy a card in advance of calling from a store or hotel. Once you've bought the card, you put it in a slot, dial the number and the total value of the call is deducted from the cash value of the card. Such cards are convenient and have the big advantage that you know exactly what you can spend in advance; but, generally speaking, cards must be bought in the country of use and are not transferable.

Credit card phones are simple variations on the basic payphone, which accept credit cards as an alternative or substitute for pre-paid cards or coins. Be careful, credit card phones may well be convenient but rack up very high charges very quickly, beginning with a high standing connection charge. Unless you are desperate, they are best avoided, particularly in airports.

Avoid collect calling (reverse charging) services like the plague - use them only where there is absolutely no alternative: they are all incredibly expensive. So-called 'home direct' (sometimes called 'country direct') options that are available from payphones around the world are also a form of reverse charging, differing only in the fact that you usually set up the call via an operator in your home country rather than locally.

Practically every major operator in the world now issues some form of calling card. These credit card-sized items basically give you a pre-assigned identity (account) number and personal identification number (PIN). In use, you call the particular operator who has assigned you the card from your location, give the identification numbers and the destination number you want, and the operator picks up your call and re-routes it to the destination. With most systems, the final bill appears in a statement from the operator or is transferred directly onto your credit card bill, so make sure you have a method of payment in place if you are travelling. The big advantage of the calling card is that it should be significantly cheaper than calling from hotel rooms, although there are wide variations in actual pricing. Because of the latter, it pays to be careful or to check charges in advance with the operator. Note also that hotels have realised that their own charging is being short-circuited by this method and occasionally engage in such tactics as charging for freephone access from rooms (many calling cards have a freephone or low-rate access for the first leg of the call into the operator), or barring the use of such numbers altogether.

Another advantage of calling cards is that they can also give you access to all the clever services that networks now offer. Most have call redirection facilities, for example, to enable automatic transfer from one number to another, conference calling for multiple users, translation and help lines.

Callback services are, potentially, the cheapest of all, with savings of between 30 to 80 per cent possible on many expensive IDD routes. They have become available as a result of the wide disparities in international calling charges. Basically, a callback service offers the opportunity for a subscriber to route his or her call through a country that can provide cheaper international access (usually this is the USA), regardless of where the call actually originated. For example, if you want to call France from India, you first notify a callback provider (perhaps in the USA) and immediately hang up. The callback service (which invariably has a pre-arranged subscription with you) then calls you back in India (hence the name), but in doing so gives you a dialling tone that enables onward dialling to the final destination (in this case, France). The call is cheaper because of the much lower rates offered by the US to India and the US to France than India direct to France.

Callback services have mushroomed in popularity due to the value they offer. Official authorities, however, are not so sure of their virtues, given that the local exchanges are clearly losing substantial amounts of revenue on this basis. Some have even resorted to means - both legal and illegal - to block callback providers or bar access to them, particularly in Argentina, Uruguay and various West African countries. China is also said to take a dim view of the service. The tactics to which such countries resort work for a time, causing everyone inconvenience, but sooner or later the callback provider has circumvented the restrictions and the process starts again.

To be sure, callback services vary in sophistication, so check the facilities on offer. You may have to designate a particular phone you will use, for example. Some providers save you the expense of calling them by automatically detecting the signalling coming from your phone system and working out the number from which you are calling before calling back. Your call is not technically connected and so you will not be charged. Cheap fax services may also be available. The major callback providers generally advertise in the main English-language newspapers around the world (at least the sort that are likely to be read by travellers). A few unscrupulous ones exist, but generally the field has a good reputation. Check the degree of your advance financial commitment - you may be asked to put down a deposit debited from your credit card, for example.

Mobile communications are on a massive roll worldwide as investors and operators see it as being a big commercial money-spinner. The cellular phone, unlike other radio systems, acts in exactly the same way as a conventional fixed phone. In terms of making or receiving calls, the systems are therefore effectively interchangeable. However, in practically every country in the world, cellular services are invariably more expensive than fixed services over the same distance (the only exception I have found is Israel, where it is possible to make cheaper long-distance calls by mobile phone than by fixed-line phones).

Now for the bad news. There is no such thing as a world standard in mobile communications, so it is not necessarily possible to take a phone from one country to another and expect it to work, a facility the industry calls 'roaming'. The nearest thing to a world standard in digital cellular is GSM (Global System for Mobile) technology, now available in more than 90 countries and used by nearly 200 operators. It is overwhelmingly dominant in Europe, the Middle East, South East Asia, South Africa and Australasia. It is therefore possible for a European to travel to Australia or a Singaporean to travel to the Middle East and, without further fuss, switch on his or her mobile phone and find it working immediately - if coverage exists in his or her location. In all these cases, the network 'knows' where the phone is when it is switched on, and manages the call routing and billing back on the subscriber's home bill. The snag is that another set of standards exists for the Americas and a third for Japan. (China, awkwardly, is a mix of standards but has established a large number of GSM networks; Russia also has several in major areas but is likewise a hotch-potch.)

However, many of the more sophisticated mobile phones now on the market have a dual-band, or even a triple-band, facility. This means that, as long as you have set up a roaming agreement with your network, your phone will work around the world. If you do want to set up this facility, leave ample time before you set off on your travels to make sure the system is in place - a couple of weeks should do it; although, theoretically, it is possible for a network to implement a roaming facility on your account within 24 hours.

A final note on roaming: expect big bills. Roaming implies that the calls you make are international calls and, as such, are charged at international rates. Even calls that appear 'local' to you in the country in which you are travelling are still treated by the network as 'international'.

An alternative to roaming, of course, would be to sign up and subscribe to the local cellular network, although this is not really worth doing unless you are spending a significant period of time in that particular country, as the contract may prove an expensive commitment. Finally, airport bureaux often offer cellular phones on a short-term basis for travellers: these will be cheaper on an overall basis than making roaming calls, but they do incur high daily charges.

Another drawback of mobile networks is a lack of coverage in the most remote areas, particularly deserts and mountains where the population is too sparse to support a mobile system economically (although you may be surprised exactly how much coverage is available). Generally, the policy of network deployment in any country is to give major cities and commercial centres the priority; thereafter, deployment is to secondary centres on a planned or phased basis.

If you thought satellite technology was really only for sophisticated expeditions, you are in for a surprise. Over the next few years a number of systems will be activated that will girdle the globe. The idea is to give coverage practically anywhere on the planet using hand-held phones that will look like and directly compete with digital cellular technology. Costs should be comparable with those of cellular systems. These could represent the biggest breakthrough of all for the independent traveller.

Data communications

The explosion of the internet has made communications by email a highly effective tool, giving you enormous facilities at very low cost. There are many email systems now in use around the world; strictly speaking, these are separate networks, but they can all 'talk' to each other and to the internet itself. Each system differs in fine detail, but all perform the same basic functions in allowing computer-to-computer communications.

It is perhaps easiest to think of such systems as being directly analogous to the postal system. Every registered email possesses an 'electronic mailbox' with a unique electronic address in which messages may be stored or received or from which messages may be sent. The advantages of email are that it is nearly instantaneous and probably cheaper on a per-message basis than ordinary post. Email is suitable for messages of almost any length, although cost varies with message size and the number of messages sent. In many cases, different types of data can be transferred over the network, including both text files produced by word processing and spreadsheet information.

At its most basic, you can gain access to your emails by routing them through a web- based Internet Service Provider (ISP), such as Hotmail, UK Smart or Talk 21. Before you set off on your travels, choose one of these providers, register an email address and notify your friends, family and colleagues of your contact details. From this point on, you can log on to a computer anywhere in the world, download your ISP page and access your email. Of course, in some countries, this is easier said than done. But many cities now have internet cafés where travellers can use the computers provided for precisely this purpose. Internet facilities are also frequently available at airports, and are a convenient way of killing time while you wait for your plane. In both these cases, you will be charged for the time you spend online. Many hotels and resorts will also provide you with access to a computer - for a price - so that you can check your emails.

The main problem with email is that, due to differences in technical characteristics, it remains generally difficult to connect a device such as a modem, specified for one country, to the PSTN or hotel room socket in another. The differences can be minor but infuriating: there are nearly 40 different types of phone sockets around the world, and even where they are physically similar, they may be wired differently. The modem dialling system may not work or may connect incorrectly because of national technical and numbering differences. There are ways around this, but you could be unlucky and find systems or hotels that are unforgiving.

That said, I have used the same laptop, modem and plug combination in hotel rooms in the UK, USA, Canada, Finland, Singapore, Taiwan and Hong Kong; with a payphone (equipped with a data socket) in Japan; and even while flying over California (with an aircraft seat phone, again equipped with a data socket). In many cases, the plug/socket combination you will require is termed RJ-11 (widespread in the USA). For hotel rooms equipped with this (and there will often be an RJ- 11 data port in the side of the phone handset), there should not be too many problems.

However, there are other problems to bear in mind. There is always a risk that hotel switchboards, more properly called 'private automatic branch exchanges' (PABXs), may be incompatible with your modem and may even damage it. The most 'difficult' travelling areas are in mainland Europe, and there may also be problems in parts of the developing world.

TeleAdapt (tel +44 20 8421 4444 or website www.teleadapt.com) is a specialist in this area, and will probably have all the information, connectors and other hardware that you will ever need. If you continue to have real problems, you may be forced to buy a modem and suitable jack in the country. Another option would be to use what is known as an 'acoustic coupler', a modem device that fits over a conventional phone handset but requires no plug and socket connection at all, but these tend to permit low connection speeds, reducing your options.

A final option - one that may prove increasingly attractive in the future - is to forget about hotel room phones, jacks and sockets altogether, and use a mobile (cellular) phone for your connection. Should you do so, you will need a special modem unit. Remember, however, that sending data over a cellular network has the same limitations as does voice communication, in that you will need a dual- or triple-band phone and a roaming agreement. A recent innovation in the world of the mobile telephone is the WAP phone, which enables direct access to the internet and email facilities straight from the handset. Although this technology is still, relatively speaking, in its infancy, it is predicted to grow exponentially and will probably become standard within the next few years, combining voice and data communications in one pocket-sized package. Watch this space.