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.

Early Nokia phones have browsers that do not support WTAI. At that time, the Nokia browser had a “Use Number” function which basically scanned 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