The PhoneBoy Blog


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How PhoneGnome and SoftGnome Work

A reader had asked me a very simple question; “How does SoftGnome utilize the unlimited long distance on your PSTN?” A relatively simple question with a simple answer: it calls the PhoneGnome over IP and gateways the call to your PSTN line. How does it do that? Read on.

Note: I do not work for Televolution, makers of the PhoneGnome, nor has anyone shared with me intimate details about what they do. The following is based on what I know about the underlying technology.

To understand why this works, first you must understand what the PhoneGnome is: a Linksys/Sipura SPA-3000 with some custom firmware controlled by the PhoneGnome servers. What is a SPA-3000? A SPA-3000 is two devices melded together: a conventional single line VoIP adapter, and a bi-directional PSTN/VoIP gateway. The “single line VoIP adapter” can use the gateway side of the device to make a call using the PSTN line. Also, the gateway side can ring the telephone connected to the single line VoIP adapter.

The basic PhoneGnome uses the gateway side of the device to divert some calls to VoIP. The anti-telemarketing feature? Calls that have no caller ID are forwarded–over IP–to another SIP server. Voicemail? After X number of seconds, the call is forwarded–over IP–to the voicemail server. The gateway also comes into play for SoftGnome specifically, and I’ll come back to that.

When you pick up the phone connected to the PhoneGnome, the dialtone you hear is virtual. It is provided by the PhoneGnome device. When you dial a number, the PhoneGnome will make a decision as to whether to send the call thru VoIP or thru the PSTN line. It does this in a simplistic manner using the digits you dial. I’ll use North America as an example since that is what I am most familiar with. If you’re dialing 7 or 10 digits, it’s most likely a local call and should go out your PSTN line. Toll-free calls (i.e. calls to 800, 888, 877, 866 area codes) are also directed out the PSTN line. Long distance calls usually start with a 1 (within North America) or 011 (international).

Long distance calls are first sent to PhoneGnome’s servers. If the number dialed is a PhoneGnome subscriber, the call will be routed over IP. If you have subscribed to another VoIP service and configured the credentials on the PhoneGnome portal, the call will be routed thru that provider. If the numbered called isn’t a PhoneGnome subscriber and the VoIP service fails, then the call will be sent via the PSTN port.

What if the power goes out? The PhoneGnome simply becomes a passthru to your existing PSTN line. While you lose all the PhoneGnome features (i.e. all the free calling and extra features), you can still use your phone to make and receive calls as normal.

What if you receive a call from another PhoneGnome subscriber? It comes in over IP to the PhoneGnome. What if you receive a PSTN call in the meantime? You can switch over to it with the flash-hook key, just like on the PSTN.

That, in a nutshell, is how PhoneGnome works, but what about SoftGnome? SoftGnome is somewhat like a conventional Internet telephony service that supports open SIP credentials. You can either use the Express Talk client provided by Televolution or you can plug the SIP credentials into your own SIP softphone, VoIP telephone adapter or IP phone. Like a conventional Internet telephony service, SoftGnome registers to a SIP proxy on the Internet. But that’s where the similaries end.

SoftGnome is an extension of your PhoneGnome. It will route calls in the same manner as it does if you were using your PhoneGnome from home. If you make a call that goes to your PSTN line, the proxy the SoftGnome talks to will call the VoIP to PSTN gateway on your PhoneGnome and route the call over your PSTN line. If the calls goes VoIP, it will connect you in the same way it does at home. Either way, it is totally transparent to you.

I think that covers the basics. If something’s unclear, drop me a line or leave a comment and I’ll do my best to clear it up.


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