Google Voice Extension for CRM

Google Voice Extension for CRM

I, like many others, use Google Voice as opposed to Skype.   I've been through older posts (some from 5 years ago) concerning the use of GV within CRM to make & receive phone calls but I'm still not clear on how to accomplish that.  Is there a native GV extension that needs to be installed through the Zoho Marketplace or does the extension need to be obtained/installed from elsewhere?

If there are detailed instructions on how to setup the use of Google Voice within CRM I would appreciate being directed to them.