URL Scheme for Phone Call

Question

Much like the "mailto" URL prefix launches the user's default mail program and starts a new email with specified address, is there a similar URL scheme that would initiate a phone call? Perhaps "phone," "call," or "sip"?

Incidentally, I'm targeting a platform that is using Cisco CUPS, so there may be a platform-specific way for me to initiate a call that is particular to Cisco, but I thought I'd ask the more general question first. However if anyone knows specifically how to programmatically initiate a call via CUPS, that would be great too.

Answer 1

sip: (or sips:) is the official URI scheme for SIP, and I think callto: is the one used by skype.

Answer 2

I'm after the same sort of functionality for Microsoft Office Communicator. After a bit of investigation I found that the following URI syntax will initiate a (VoIP) phone call via communicator:

tel:+number

eg: to get communicator to call my extension:

tel:+7780

Answer 3

http://www.ietf.org/rfc/rfc3966.txt

Answer 4

The official standard is here: http://www.ietf.org/rfc/rfc3966.txt

It basically says use tel: as the prefix, and start the number with +[international dialling code] before the number itself. You can put non-numeric characters as separators (e.g. -) but they must be ignored. So a London (UK) number might be:

tel:+44-20-8123-4567

A New York (US) number:

tel:+1-212-555-1234