Separate a telephone identifier from a dial string
01A tel URI identifies a telephone number. The application supplies the local dialing procedure, and reaching a real endpoint is a separate task.
In one illustrative environment the application might produce 00 1 201 555 0123. That is a local procedure, not an alternative tel URI or a successful-call result.
Key idea: A telephone number is an identifier; dialing steps depend on the application and its environment.
Terms
- tel URI
- A Uniform Resource Identifier for a telephone number. tel names the telephone scheme; it is not an instruction to dial.
- Global number
- A number written with a leading + and its international country and national number.
- Local number / context
- A number meaningful within an identified scope, such as a private phone system. The context distinguishes otherwise identical local numbers.
- Dial plan
- Application configuration that translates number identifiers into local dialing procedures. A particular prefix is not universal.
Rules & examples
A telephone number is an identifier; dialing steps depend on the application and its environment.
- The tel URI is a globally unique identifier, not a sequence of dialing actions and not a reference to one particular physical device. It does not specify the call type, such as voice or fax.
- A dial string may include an outside-line digit, an international access prefix, pauses or post-dial tones. Those procedures are outside RFC 3966; do not copy them into a tel URI as if they were the number.
- The dialing application or gateway converts the identifier to an appropriate procedure using its own configuration. The illustrated 00 prefix belongs only to the chosen local dial-plan example, not every country or phone.
- A unique identifier does not guarantee that the number is assigned or reachable from a particular location. Web clients MUST NOT place calls without explicit user consent (§11). No example here performs a real call.
Fictional offline examples only: no dialer is opened and no call is placed. URI syntax does not verify number assignment, reachability, ownership or caller identity. Selected examples are not a complete telephone or SIP implementation.
Sources
New to this? Start hereA quick picture + helpful background
A number is not a dialing procedure
Think of a contact card: it names who to reach, while the phone system supplies the steps for making a connection. A tel URI similarly identifies a number; its context and parameters help interpret it but do not authorize a call or promise reachability. This is an analogy, not a telephone-routing algorithm.
Helpful first, if these ideas are unfamiliar
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.