Connecting a VoIP System to the PSTN

May 25, 2010 by Brian Hyrek

The PSTN still (believe it or not) has its place in today’s telecommunications world.

With communications being the “beating heart” of your business, you certainly cannot afford to be without the ability to send and receive valuable phone calls. It is possible, with VoIP, that your network crashes or Internet connectivity can be lost. Meaning, of course, the your ability to send or receive calls, emergency included, is stripped.

That’s the problem and I herein present you with the solution: an FXO VoIP Gateway!

In one of my previous posts, I had skimmed the term FXO. FXO (Foreign Exchange Office), designates a telephone signaling interface that receives POTS (Plain Old Telephone Service). FXO generates the off-hook and on-hook indications. Basically… an FXO device is one in which appears to be a “regular telephone”. An FXO device would be able to accept ringing signals, go on-hook/off-hook, and send/receive voice frequency signals.

So what do I actually use this gateway for and why?

Well, there are more than a few applications for an FXO gateway but I will just name the most common (I’m sure you’ll be able to get a bit creative with these devices).

  • Failover– What if my SIP provider is experiencing problems, what if my network crashes? These are a few common questions that I hear time and time again. Luckily, an FXO creates the perfect solution/failsafe. An FXO gateway can be implemented to provide access to multiple POTS lines (the gateways normally come in 2,4, and 8-port flavors).
  • Bringing In local analog POTS/PSTN lines from remote locations to be utilized by IP PBX at the central location – Example; say your main site is in NY and you have remote locations in CA and TX. In using an FXO gateway, you can utilize local landlines from remote locations ( CA and TX) to be utilized by the main site’s IP PBX. Phone calls from NY pass through the internet (VoIP) to the remote locations to make locals calls that corresponds to each location. Local telephony companies for these locations will “think” the calls are local as the calls are rolling out from the FXO gateways at each location and nothing will appear to be of long distance. Now how cool is that?!?

Analog VoIP Gateways enable flexible deployments and interoperability for evolving next generation networks. Supported protocols for Analog gateways include SIP and certain gateways even provide support for lesser used protocols such as H.323. and MGCP.

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