--- title: "ITU roles and numbering plans" subject: "Telecommunications" chapter: 7 key: "semester_8/telecommunications:itu-roles-numbering-plan" source: https://www.bctengineer.com/q/semester_8/telecommunications/itu-roles-numbering-plan site: BCT Engineering --- # ITU roles and numbering plans Telecommunications · Chapter 7: Telecommunication Regulation - Asked in: 2075 Asoj, 4+4 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/telecommunications/itu-roles-numbering-plan - Whole chapter: https://www.bctengineer.com/md/semester_8/telecommunications/chapter-7 ## Question What are the roles of ITU? Explain numbering plan for national and international telephony systems. ## Short answer ITU manages radio spectrum (ITU-R), sets worldwide standards (ITU-T) like E.164, assists developing countries (ITU-D), and assigns country codes. A national numbering plan uses a trunk prefix, area code, and subscriber number; the international plan (ITU-T E.164) uses an international prefix “+”, a country code, and a national significant number, with a maximum length of 15 digits. ## Answer #### Roles of ITU The **International Telecommunication Union (ITU)** is the UN specialised agency for ICT, founded in 1865 and based in Geneva. Its roles are: 1. **Radio spectrum and orbit management (ITU-R):** allocates frequency bands and satellite orbit slots worldwide and maintains the Radio Regulations to avoid interference. 2. **Standardization (ITU-T):** develops Recommendations such as E.164 (numbering), G.711 (PCM), Q.700 (SS7), H.323, so that networks and equipment work together worldwide. 3. **Development (ITU-D):** helps developing countries with infrastructure, policy, regulation and training; works to bridge the digital divide. 4. **International numbering and tariffs:** assigns country codes and sets accounting principles for international calls. 5. **Cooperation and safety:** promotes international cooperation, emergency telecommunication, cybersecurity and accessibility. #### Numbering plan A **numbering plan** gives a unique number to each subscriber and fixes the digits used for routing and charging. **National numbering plan** ```text [Trunk prefix][Area code][Exchange code][Line no.] 0 1 44 12345 ``` - **Trunk prefix** (0 in Nepal) for long distance calls. - **Area / national destination code (NDC):** e.g. 1 Kathmandu, 61 Pokhara, 21 Biratnagar; mobile codes 984, 980. - **Subscriber number:** exchange code + line number. - **Open plan:** short local numbers, prefix + area code for other areas (Nepal, India, UK). - **Closed plan:** fixed-length number always dialled (USA, 10 digits). **International numbering plan (ITU-T E.164)** ```text [Intl prefix][CC][National significant number] 00 977 1 4412345 ``` - **International prefix:** 00 (011 in North America), shown as "+". - **Country code:** 1–3 digits; first digit is the world zone (1 North America, 2 Africa, 3/4 Europe, 5 Latin America, 6 Oceania, 7 Russia, 8 East Asia, 9 Asia/Middle East). - **NSN:** national number without the trunk prefix. - Maximum international number length: **15 digits**. | Call type | Dialled from | Digits | |---|---|---| | Local | Kathmandu | 4412345 | | National | Pokhara | 01-4412345 | | International | abroad | +977-1-4412345 | ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which ITU-T Recommendation defines the international numbering plan? A. E.164 B. G.711 C. Q.700 D. H.323 Answer: A. E.164 is numbering; G.711 is PCM, Q.700 is SS7 and H.323 is multimedia signalling. (Key point: ITU-T Recommendations) 2. What distinguishes a closed numbering plan from an open one? A. Closed uses variable-length numbers with area-code prefix only for other areas B. A closed plan is used only internationally C. A closed plan has fixed-length numbers that are always dialled in full (e.g. USA, 10 digits) D. A closed plan has no area codes Answer: C. Open plans allow short local numbers with prefix plus area code for other areas; closed plans use fixed-length numbers. (Key point: Open vs closed numbering plan) 3. Which sequence correctly forms an international number under E.164? A. Trunk prefix, area code, subscriber number B. Country code, trunk prefix, 15 digits C. National significant number, then country code D. International prefix, country code, national significant number (without trunk prefix) Answer: D. The NSN is the national number without the trunk prefix, preceded by the country code and international prefix. (Key point: Structure of international number) 4. What is the maximum length of an international number in E.164? A. 10 digits B. 15 digits C. 12 digits D. 20 digits Answer: B. E.164 limits international numbers to 15 digits. (Key point: Maximum length) ## Related in Telecommunications - [National and international numbering plans](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Anumbering-plan-national-international) — Telecommunications, chapter 7, asked 3× - [NTA's role and ITU numbering plan](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Anta-role-itu-numbering) — Telecommunications, chapter 7 - [Traffic intensity, GOS and national numbering](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Atraffic-intensity-gos-numbering) — Telecommunications, chapter 6 - [Roles of NTA and ITU](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Anta-roles-itu-roles) — Telecommunications, chapter 7