Cisco Systems, the Internet communications giant, said it has agreed to acquire privately held San Jose company Orative Corp for $31 million — as part of its effort to offer the so-called quadruple play: voice, video, data and mobility to businesses.

Earlier this year, Cisco Cisco launched what it called the “Unified Communications system,” which enables businesses of all sizes to integrate all of their communications systems with their IT infrastructure.

Orative’s technology allows Cisco to extend the capabilities of unified communications to mobile devices such as cell phones and smartphones.

Orative has 33 employees, and had raised $18 million since being founded in 2003 — so the deal is a so-so outcome for Orative’s investors: Trinty, Mayfield, Diamondhead Ventures and Stanford University.

From the company’s statement:

The Cisco Unified Communications system of voice, video and IP communications products and applications enables organizations to communicate more effectively by leveraging all services located in the network from anywhere, with any device, at anytime.

…With Orative Enterprise Software, mobile phone users can coordinate conversations, collaborate with colleagues, view information on Unity voicemail messages, screen unwanted telephone calls and interruptions, and securely access personal and corporate phone books. Together, Cisco and Orative will transform the mobile phone into a true business device, using Cisco Unified CallManager for call control, Cisco MeetingPlace for collaboration and Cisco Unity as the voicemail platform.