Browsers that support all or parts of the so called WTAI specifications have a function that lets you link to a telephone number. The function is explained here.

At the time of writing, no Nokia phone have browsers that support WTAI, and although this is likely to change, there is currently no way of linking to a telephone number in the same way WTAI supports. Instead, the Nokia browser has a "Use Number" function which basically scans through the current WML deck looking for something that resembles numbers which it displays in a list. The number can then be dialed by pressing the "Off hook" button.

In some cases this function is a bit tricky to incorporate into a WML deck, especially if you want to use the same deck for browsers that support this WTAI function, and those that don't. A method of presenting the number only once in a deck but still support both types of browser has not been found, instead, you will have to display the number twice, or, have the server detect if it is a WTAI compatible browser and generate a deck based on this.

It is important that you understand how numbers are recognized, and the following example should give you an idea. Note the way (some) non-numeric characters right next to numeric characters influence the recognition. Also note that the number inside the link hides the number completely.

<p>+1 234 567</p>
..gives "1234567"
<p>(01)234-567</p>
..gives "01234567"
<p>(01) 234-567</p>
..gives "234567"
<p><a href="call.wml">234-567<a></p>
..would not give anything at all