TelTel COO Jack Chang calls his vision for the future of communications the PSIPTN. It’s not just cute. It telegraphs Chang’s essential axioms.

First, Internet telephony needs to be as plug-and-play as POTS for consumers. Second, down the road we’re not going to be talking about the merits of competing multi-media IP protocols any more than we’re talking about the merits of competing analog telephony protocols.

“SIP is similar to the PC world in the early 80s,” Chang says. “More and more applications are becoming SIP-compliant. Cisco earlier this year announced adoption of SIP.”

With an estimated 2 million registered international users for its VoIP service, TelTel is probably one of the best-kept secrets in VoIP, By comparison, Jeff Pulver’s much better-known Free World Dialup, has some 600,000 users.

But Tel Tel is working hard to get consumer attention. The service is adding 100,000 users a month and is the world’s largest SIP-based user community, according to Chang. In March, TelTel introduced a sleek D-Link flip-style WiFi handset that retails for about $200.

The company’s service and business model is virtually identical to Skype’s. But Chang is banking on SIP’s open-ness to beat Skype at its own game and he’s evangelical about the possibilities of the SIP ecosystem.

“People think that VoIP is all about making cheap calls,” he says. “While we don’t disagree, VoIP is about a lot more. Vonage’s business model depends on the PSTN. We think that calling the PSTN is a ‘necessary evil.’ For the company to grow, we cannot depend on that.”

Instead, the company’s long-term goal is providing the backbone for businesses to deliver all kinds of services over the Internet.

“Our philosophy is to promote on-Net traffic and generate revenue from on-Net traffic, to be a platform for a new generation of services. Once you have all these devices using SIP, it opens up a lot of services — video, gaming, conferencing,” Chang says, using as an example is a surveillance camera that makes a phone call and emails a video when it detects motion.

In addition to its embrace of SIP, there is another important difference between TelTel and Skype. TelTel uses a managed peer-to-peer network. “With Skype’s peer-to-peer [model] there is no management for voice packets,” explains Chang. “Voice quality can’t be guaranteed. TelTel uses special servers to ensure QoS.”

TelTel is the second company started by entrepreneur Sherman Tuan, whose IT service company AboveNet went public in 1997 and was subsequently bought by Metromedia Fiber Networks.

Chang is also a serial entrepreneur. He founded Blue Silicon, a provider of hosted unified and multi-media messaging, and Carmel Connection a manufacturer of corporate voice, fax and mail products.

After AboveNet, the growing opportunities presented by the Internet beckoned to Tuan. “We wanted to take advantage of the Internet as it is today — ubiquitous,” says Chang.

The company debuted its VoIP service in 2004 and currently employs about 60 in its Santa Clara, CA headquarters as well as an overseas support and operations team. TelTel also offers its service to service providers as a private branded service.

Mac users are like cats - famously contrarian about following the herd. And with the herds rushing to Skype, your typical Mac user will start heading off into some other direction.

London-based Woize (pronounced woy-zee) is targeting this herd of cats with its SIP-based, peer-to-peer VoIP client for Mac OSX, announced yesterday. The company says that the beta version of the software will be released sometime before the end of the year.

The features are pretty comparable to Skype. Calls between Woize users are free, with charges for calls to landline and mobile phones. The company already offers VoIP clients for Windows - including Windows Mobile - and an ATA that lets you use your telephone to make Woize calls.

The main advantage of Woize’s approach is, because it’s SIP-based, Woize users can connect with other SIP users.

“SIP is the not only the future of communications. it is quickly becoming the cornerstone of IP communications as we know it today,” says Erik Lagerway, author of the SIP That and CTO of Shift Networks. “Proprietary solutions are not a viable long term solution and will not impact the future of SIP.”

But Woize is hardly the first one out of the box with a solution to compete with Skype. TelTel of Santa Clara, CA has been offering its SIP-based softphone for over a year now. TelTel claims about two million registered users and is adding about 100,000 users a month, according to CEO Jack Chang.