Hi Jose,

CME support for SIP was first introduced in CME 3.4 and has evolved through CME 4.1 Have a look at the following;

CME 3.4

http://www.cisco.com/en/US/products/sw/voicesw/ps4625/prod_installation_guide09186a008055677f.html

Cisco Unified SIP IP Phone 7905G and Cisco Unified SIP IP Phone 7912 for Cisco CallManager Express 3.4

http://www.cisco.com/univercd/cc/td/doc/product/voice/its/cme34/cme34rc1.htm

Cisco Unified SIP IP Phone 7960G and Cisco Unified SIP IP Phone 7940G for Cisco CallManager Express 3.4

http://www.cisco.com/univercd/cc/td/doc/product/voice/its/cme34/cme34rc2.htm

CME 4.1

SIP Features for Cisco Unified CME 4.1,

http://www.cisco.com/univercd/cc/td/doc/product/voice/its/cme41/cme410ft.htm

How to Configure SIP Features for Cisco Unified CME 4.1

http://www.cisco.com/univercd/cc/td/doc/product/voice/its/cme41/cme410ft.htm#wp1049437

Hope this helps!

Rob