Tel: ist not used on phone numbers

I have upgraded to the latest suitecrm release .21 because before I could not use click-to-dial before and thought this could help. But still after upgrade on the phone number the phone number will not show up as tel: so that I can use click to call (even my voip switch support it).
It only shows e.g. on contacts: mydomain/index.php/action=ajaxui#
What can be the reason?
Did someone else has a similar behavior.
Thanks for your help.

With some modifications in the right places, you can get this to work.

go to <SUITE_DIR>/include/SugarFields/Fields/Phone/EditVIew.tpl and change the type from text to tel

then go to <SUITE_DIR>/include/SugarFields/Fields/Phone/DetailVIew.tpl and change
{sugar_phone value=$phone_value usa_format="{{if !empty($vardef.validate_usa_format)}}1{{else}}0{{/if}}"}

to look more like (example not tested, quick write up)

<a href='tel:{sugar_phone value=$phone_value usa_format="{{if !empty($vardef.validate_usa_format)}}1{{else}}0{{/if}}"}'>
anchor text goes here
if you want it to be the phone number then replace this message with
{{if !empty($vardef.validate_usa_format)}}1{{else}}0{{/if}}

The same can also be done with the Int field type, where you can change the input type from text to number

thanks a lot for your quick reply.
What I am asking myself is: I read that tel: was implemented some releases before,

I also looked at a demo of 7.10.24 and in the 8 beta and on both installations the phone number is as tel: clickable. So something must be wrong with my installtion. On these demos it even works in the list view. So how can I fix my installation to get it to work on every place.