To many Americans, going wireless with a cell phone or tablet while in Europe can seem difficult and expensive. But savvy travelers know it doesn't have to be. Having a phone while you're there can be a major time saver and convenience. This article tells you how to stay in touch and save money. [This is part 1 of 2 articles: the second covers cellular data in Europe] Why don't US cell phones "just work" in Europe? For various reasons, the United States developed and deployed wireless technologies that were incompatible with those deployed in the Rest Of the World, which went with a standard called GSM ("Global System for Mobiles" - one of the reasons why Europeans use the term "mobile" and not "cell phone"). This meant that for many years, the only option for US travelers to Europe was to rent a GSM phone, which was expensive and inconvenient. No one could reach you on your US cell phone number; you had the hassle and cost of receiving and returning the phone, and both phone rental and calls were astonishingly expensive.