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

Research in Motion says yes. RIM has 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 US autumn, 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.

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 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.

But aren't all the vendors trying to do this? None of them say 'our design goal is to make it completely non-intuitive...'

What's fundamentally different is, if you hand someone a BlackBerry smart phone for the first time and say "make a call", they'll work it out very quickly. Other solutions may require you to know, for example, there's a new program that you have to call up, or create new calling lists, and run through some kind of manual process. Our solution appears just as part of the user's existing phone experience. Anything less than will not be adopted [by users].

I know I don't use many PBX features on my office phone. Are your enterprise customers really impressed with this?

When I've shown this, I've had some jaws drop and people say "I never thought you could do that". The security and GUI improvements we're introducing with MVS came straight out of talking to customers. BlackBerry MVS is the voice analog of BlackBerry Mobile Data Service, which is about mobilizing the enterprise data stores, starting with e-mail.

You mentioned security. What's actually new here?

The innovation is in user authentication. One large bank explained it well: They have many voice-enabled services in their PBX infrastructure, accessed by executives and others. They can't allow a mobile device user to get access to things like directory lookups, long-distance dialling, and so on, because they can't authenticate the device's user.

Surely there was some way to authenticate in the past?

To enable this in the past, you were using Automatic Number Identification (ANI), as your caller ID. The PBX would give the OK based on the ID. But spoofing this is very, very easy. The other method is using a PIN number like you do with your ATM. But the user has to enter the PIN manually or it's part of the dial string. In either case, it can be cracked.

So how do you do it?

The BlackBerry devices are already secured and trusted. The device sends an encrypted datagram to the BlackBerry Enterprise Server. Then we authenticate the user, and finally make an outbound call from the PBX to a known phone number. They've not used ANI or a PIN to gain access to the PBX.

Does this mean the end of the desk phone?

The average lifecycle for a PBX is 8.5 years. So you won't see anything that dramatic. But for the 30% of people who are highly mobile, and rarely at their desk, MVS is enabling more functions for them.

When are you releasing BlackBerry MVS and how much will it cost?

Later this May. We've not release pricing. Stay tuned.

Are you using a BlackBerry phone and your PBX for this call?

I'm using a BlackBerry Curve, on speaker phone. We're in a conference room with a land line that's not very reliable.

Is the Curve linked with the PBX?

[Heather Howland, senior manager for Ascendent marketing] It's my phone, a trial device, so it's not integrated with the PBX yet.