The acronym IDD has two meanings in the realm of technology. On the one hand, it can refer to an Instant Daytime Dialer™, a software tool that assists in telephonic client contact. The other meaning of IDD is International Direct Dialing. This refers to a method for direct international calling not facilitated by an operator that the International Telecommunication Union (ITU) promulgated in standard E.164.
The IDD calling system from Client Instant Access™ streamlines the work of those who have to make many calls, leaving messages at a large number of them. The system uses a pre-recorded message when it reaches voicemail, but passes the call to an attendant if the call is answered. Because it can handle voicemails, it therefore can operate without an attendant’s full attention. It also avoids the strain of many repeats of a message and ensures that every message has the same tone and feel. Calls can be personalized, even when a recorded message is used.
ITU is a United Nations agency that is tasked with allocation and standardization of the radio spectrum and creating the organizational basis for international telephone calls. The IDD prefixes, sometimes called international call prefixes, are for calling out of a country, and must be combined with country codes; people have been known to confuse the two. While the general standard suggested by ITU is 00 for a prefix, countries have made alternative choices, and the symbol + is used as a placeholder.
The assignment of zones for country codes is laid out as follows, as of 2005. Zone 1 covers Canada, the United States, the US Pacific territories, and a number of nations in the Caribbean. Zone 2 is mainly African countries, Zones 3 and 4 are Europe, and Zone 5 includes Mexico, Central America, South America, and the West Indies. Zone 6 includes the South Pacific and Oceania, while Zone 7 includes Russia and Kazakhstan. Zone 8 is for East Asia and special services, such as the Mobile Satellite System and Maritime Mobile Service. Zone 9 covers West Asia, South Asia, and the Middle East, while Zone 0 is not assigned.
To place an international call by IDD, one begins with the prefix for calling out of one’s own country. This can be found in a telephone book or on the Internet. For example, the United States IDD prefix is 011. Some phones allow the dialer to simply save the + along with a phone number, and the phone then converts the + to the proper prefix when dialed. One follows this with the country code for the country one is calling, and for the United States, this would be 1, a country code it shares with a number of other countries, including Bermuda, Canada, Jamaica, Guam, and Montserrat. One then continues with the city or area code, if applicable, and the phone number. Some countries, particularly small ones, do not use city or area codes, and these numbers are the most likely parts of the system to change.