How Telephone Country Codes Work

By: Dave Roos

The Telecommunication Standardization Sector

­As business professionals travel more, they rely on calling codes to make international calls so they can stay in touch with home and office.
© Andrew Lichtenstein/Getty Images

The Telecommunication Standardization Sector is part of the International Telecommunication Union (ITU), an agency of the United Nations. The ITU, based in Geneva, Switzerland, works with 191 member countries to develop and implement global communications technology.

The specific responsibility of the Telecommunication Standardization Sector (ITU-T) is to research and recommend standards and protocols relating to voice and data transmissions over landline and mobile networks. This includes everything from streaming video on cell phones to Voice over IP (VoIP) to SMS to international call rates.


When it was established in 1925, the  ITU-T was called the Comité Consultatif International Téléphonique et Télégraphique (CCITT). The CCITT was responsible for breakthrough work in standardizing fax data transmissions, modems, data compression, packet-switching and e-mail. The CCITT became the ITU-T in 1993 as part of a new strategic plan to respond quicker to the ever-changing technological landscape [source: International Telecommunication Union].

The ITU-T is best known for its recommendations. As their name implies, recommendations aren't laws or regulated standards, but merely suggestions for the best way to make telecommunications technology and networks run smoothly. Recommendations are established by 13 study groups within the ITU-T. Each study group is comprised of international managers and rapporteurs (appointees) from the public and private sector. A typical study group might include a CTO from Israel, a researcher from Germany and an American policymaker from the Federal Communications Commission.

Study groups are assigned a handful of questions, which they research over the course of two to four years before publishing their recommendations. Questions resemble topics. Current examples of questions include:

  • Optical fiber cable network maintenance
  • Traffic engineering for mobile communications
  • Voice and video IP applications over cable television networks
  • Real-time audio, video and data communication over packet-switched networks

The ITU-T also organizes focus groups, which are smaller research units within a study group working on a specific problem or question. Recommendations are published online and are free to the public as well as private industry and government agencies.

Next let's talk about the ITU-T recommendation that established the current international numbering plan.