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NXXstands forNumbering Exchange Code
Full Form of NXX
What is NXX?
In the Indian telecom numbering plan, an NXX (Numbering Exchange Code) refers to the three-digit exchange code that, together with the STD (Subscriber Trunk Dialing) code, uniquely identifies a specific telephone exchange within a geographical area. For landline numbers, the NXX forms the first three digits of the local number after the STD code, routing a call to the correct exchange. For mobile numbers, the first four digits (including the operator code) serve a similar purpose, though the term NXX is historically more associated with fixed-line systems. The Department of Telecommunications (DoT) allocates NXX blocks to telecom operators to ensure efficient call routing and numbering resource management. NXX codes are critical for implementing number portability and inter-carrier connectivity. Students of telecommunications engineering or those preparing for exams like GATE, IES, or BSNL recruitment often encounter NXX as part of PSTN (Public Switched Telephone Network) basics. Understanding NXX helps in grasping how calls are switched across exchanges, and it forms the foundation for more advanced concepts like SS7 signaling and number translation. In rural areas, NXX codes also facilitate the expansion of telecom networks by organizing local exchanges.
NXX का फुल फॉर्म
नंबरिंग एक्सचेंज कोड
Example
The telephone number 011-12345678 uses the STD code 011 for Delhi and the NXX code 123 to route the call to the Karol Bagh exchange.
NXX — frequently asked questions
What is the full form of NXX?
NXX stands for Numbering Exchange Code. It is a three-digit exchange code used in Indian telephone numbering plans to identify a specific local exchange.
How is NXX different from STD code?
The STD code identifies the geographical area (city or region), while the NXX code identifies the specific exchange within that area. Together they form a complete routing path for landline calls.
Is NXX used in mobile numbers?
The term NXX is primarily used for fixed-line numbers. Mobile numbers use a different numbering structure where the first four digits represent the operator and circle, though the concept of an exchange code is analogous.