E.164 numbers and direct inward dial

• Wikipedia says E.164 is the ITU-T recommendation titled The international public telecommunication numbering plan.
• It says plan-conforming numbers use only digits and a maximum of fifteen digits, with a country code of one to three digits.
• The ITU page that opened lists E.164 (02/26), The international public telecommunication numbering plan, as an in-force component.
• Direct inward dial, on its article, is a service for PBX subscribers: many numbers over trunks, and the dialed number is transmitted so an extension can be reached directly.
• The same article says the dialed number is signaled with DNIS, often in a partial format such as the last four digits.

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