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Reserved Number Space

The following numbers should not be assigned within a domain because they are reserved for system functions.

011 + any number of digits011 is used to prefix international dialing. Note: Custom programming will not work for this number space.
211Community Information and Referral Services
311Non-emergency municipal government services. Only supported in certain major cities.
411Information
511Traffic and Transportation Information (US); Provision of Weather and Traveller Information Services (Canada)
611Customer Service
711Telecommunications Relay Service (TRS)
811Call-before-you-dig - Access to One Call Services to Protect Pipeline and Utilities from Excavation Damage (US); Non-Urgent Health Teletriage Services (Canada)
911Emergency
933911 Test Number
988National Suicide Prevention Hotline