Google is simplifying the setup for tracking website call conversions in AdWords.
The initial setup is the same, with the option to set up website call conversions under the Conversions section of AdWords.
Now, instead of having to add a tag each time a phone number is listed on the landing page, you only have to add one piece of conversion tracking code on your site.
Google says the new process is designed to support tracking for one phone number. You can find more details on the support page.