Can you trust the folks who recently brought you a 12-hour wireless e-mail outage to bring your cell phone to the corporate PBX?

Research in Motion says yes. RIM this week introduced what it’s calling the BlackBerry Mobile Voice System (MVS), which provides a way to marry BlackBerry smart phones with corporate PBX telephony systems.

That means you can give people a single, unique phone number to call, and have calls ring simultaneously on your BlackBerry, your home-office phone, and the wired clunker on your desk at headquarters. In addition, you can use the BlackBerry user interface, trackball, buttons, menus, and all that neat stuff to hold, transfer or conference a call, or find a number in the corporate directory.

Other vendors such as Siemens and start-ups such as DiVitas Networks also are trying to converge fixed and mobile telephony. Last fall, Cisco acquired Orative for the same reason.

MVS consists of new code added to the BlackBerry Client, which runs on the BlackBerry smart phone, and to the BlackBerry Enterprise Server (BES), which manages a bunch of BlackBerry wireless services, including e-mail, through the corporate firewall. The third component is an existing product, the Ascendent Voice Mobility Suite, which is server software that works with an array of third-party, enterprise TDM and IP PBXs. RIM acquired Ascendant Systems in 2006.

To find out how this magic works, Network World Senior Editor John Cox talked with Theron Dodson, director of sales and marketing at RIM’s Ascendent Systems subsidiary -- who carries a BlackBerry 8700, an 8800, and the sexy brand-new BlackBerry Curve smart phone.

So what goes where and what happens?

The Ascendent Voice Mobility Suite software sits on a server and interfaces to whatever PBX you’re using. It’s extending PBX functions to the mobile devices. The server stores a profile of the user, which includes numbers for his desk phone, BlackBerry phone, home-office number and so on. When a call comes in to the PBX, it looks to the Ascendent software for guidance, and then simultaneously rings all of those numbers. When you answer the call with, say, your BlackBerry, the other calls drop.

If I want to call out from my office, using my BlackBerry smart phone, how does that work?

You dial the number on the BlackBerry. It uses the data channel on the wireless carrier’s net to push a very short encrypted data message to the BlackBerry Enterprise Server behind the firewall and to the Ascendent server. It’s the same data channel used by BES today for e-mail. The PBX then places your call to the other party over its PSTN interface, initially it’s wireline and then goes cellular. It makes an authenticated call to your BlackBerry device and then the PBX bridges in the other party.

Wouldn’t that approach add latency?

The data channel is pretty quick. There’s not a lot of data latency. And your typical GSM call setup is 8-10 seconds anyway. “Dial-tone” doesn’t mean the same thing in mobile as it does in your landline.

Click to see: Screenshot: RIM's BlackBerry client

Did your software engineers actually write new code for MVS?

Absolutely. Ascendent had a shipping product in the market. It was being distributed through wireless carriers. We heard from enterprise customers that they wanted to authenticate smart phone users and make the smart phone easy to use and administer. So we changed the BlackBerry phone client and created a new file that’s pushed down to the devices from the BlackBerry Enterprise Server’s “Service Book,” which is used to control the client devices. This new file enables the Ascendent functions which are now all native to the BlackBerry client. The device just turns on one day and users don’t know the difference.

I still can’t transfer a caller from my desk phone at the Network World office. How easy, really, are these PBX functions on the BlackBerry?

How many times have you said or heard, “I’m going to try to conference you, but if I hang you up, call me back?” You can look up the zip code in Zimbabwe but you can’t phone conference with the guy in the next office. We wanted to make these functions simpler than they are on for most people [on desktop phones]. So, on the BlackBerry, you’d push the trackball, see the menu, see “Transfer,” do a ‘rollover’ to find ‘Heather Howland’, click on her name, click again and it transfers. The same kind of thing happens for ad hoc conferences. If you’re on the road, you hit “*1” and dial Heather. It rings her phone, she jumps on the call, you click “conference,” click another name, and [our software] pulls you all together. A main design goal for us was [that] we tried to think through how people actually use this device and make it completely intuitive for them to do it.