Usage is listed in the NANP as follows:
- 2-1-1: Community services and information (eg: United Way of America)
- 3-1-1: Municipal government services, non-emergency number
- 4-1-1: Directory assistance
- 5-1-1: Traffic information or police non-emergency services
- 6-1-1: Telephone company (telco) customer service and repair
- 7-1-1: TDD and Relay Services for the Deaf and Hard of Hearing
- 8-1-1: Underground public utility location (United States); non-emergency health information and services (Canada)
- 9-1-1: Emergency services (police, fire, ambulance/rescue services)
Each of these eight numbers is part of a NANP dial plan using NPAs (Area Codes) which prevent nearly 8,000,000 telephone numbers (from N11-NXX-0000 to N11-NXX-9999 excluding certain NXXs) from being assigned.
The assigned use of each N11 can vary for the various countries included in the NANP but 9-1-1 is mandated in the U.S. and Canada, while the availability of the other N11 codes varies by location. 7-1-1 and 9-1-1 access is mandated by law in the U.S., even within private networks (PBX, Enterprise and Cellular systems). Cellular services often cannot automatically provide a specific location of a caller using 9-1-1.
4-1-1 and 6-1-1 are supported by the service provider for the calling phone but not all carriers provide these services. 4-1-1 and 6-1-1 (formerly 8-1-1) are typically blocked within Enterprise or PBX systems (including Cellular service purchased for an Enterprise System) since generally, 4-1-1 calls incur a fee and the service is now readily accessible by other means and 6-1-1 services are managed by the Enterprise the phone resides in.
Other community services are provided through 2-1-1, but only if a non-profit organization such as the United Way or the local government operates it locally. Likewise, local or state/provincial government may, but do not uniformly, operate traffic information using 5-1-1. 8-1-1 was made mandatory in the U.S. in 2007; however, it has not been universally been implemented. 7-1-1 is funded through the TRS Fund which Telco Carriers are mandated to maintain to provide Relay Services for the Deaf and Hearing Impaired.
0-1-1 & 1-1-1
Within the NANP, a leading digit of 0 or 1 indicates special dialing arrangements such as 0-1-1 followed by a country code is used to dial internationally or 1 followed by a 10-digit phone number indicating long distance or toll charges. In a few states, some areas retain the ability to use 7-digit dialing for local calls, in these areas a leading digit of 1- must be followed by a 10-digit phone number. As such, N11s are restricted by NANP design to N = 2 through 9 creating the 8 allowable N11s. This is also why NPAs (Area Codes) or 7-digit phone numbers (designated by NXX-XXXX) cannot have a 0 or 1 as the first digit (N).
- Single Non-Emergency Number, used in the United Kingdom
- See FCC Doc. No. 92-105