From W3C Wiki
The telephone state represents a control for editing a telephone number given in the element's value.
- Unlike the URL and E-mail types, the Telephone type does not enforce a particular syntax. This is intentional; in practice, telephone number fields tend to be free-form fields, because there are a wide variety of valid phone numbers.
autocomplete= on/ off/ defult
The on state indicates that the value is not particularly sensitive and the user can expect to be able to rely on his user agent to remember values he has entered for that control.
The off state indicates either that the control's input data is particularly sensitive (for example the activation code for a nuclear weapon); or that it is a value that will never be reused (for example a one-time-key for a bank login) and the user will therefore have to explicitly enter the data each time, instead of being able to rely on the UA to prefill the value for him; or that the document provides its own autocomplete mechanism and does not want the user agent to provide autocompletion values.
The default state indicates that the user agent is to use the autocomplete attribute on the element's form owner instead. (By default, the autocomplete attribute of form elements is in the on state.)
list= ID reference
Identify an element that lists predefined options suggested to the user.
If present, its value must be the ID of a datalist element in the same document.
maxlength= positive integer
Gives the maximum allowed value length of the element.
Gives the name of the input element.
Specifies a regular expression against which the control's value is to be checked.
When an input element has a pattern attribute specified, authors should include a title attribute to give a description of the pattern.
Represents a short hint (a word or short phrase) intended to aid the user with data entry.
A hint could be a sample value or a brief description of the expected format. For a longer hint or other advisory text, the title attribute is more appropriate.
Controls whether or not the user can edit the form control.
When specified, the element is required.
size= valid non-negative integer
The number of options meant to be shown by the control represented by its element.
Gives the default value of the input element.
<label>Phone: <input type="tel"></label>
The HTML5 specification defines the Telephone state in 220.127.116.11.3 TELEPHONE STATE.