An ITSP is an Internet Telephony Service Provider which means that they have gear that can translate phone calls from packets that travel over the Internet to audio calls that travel through the PSTN (Public Switched Telephone Network). The PSTN is what the phones in our house used to be connected to and has been around since the 1870’s. It requires only two wires to work and has both 48V DC to power the device and the analog audio superimposed on the same wires. In order to cause the phone to ring a 90V AC signal is applied to the wires. I could on to describe in detail how legacy phones work, but it really doesn’t matter any more because they will all be replaced in the next decade or so.
Cell phones have been replacing legacy home phones (or landlines) even though they tend to cost a bit more to operate. The mobile nature of the cell phone, makes it much more attractive to the current generation. Some people however are not ready to cut the cord and have migrated to VoIP (Voice over Internet Protocol). This means that there has to be a translation between the legacy phone sets to convert the analog signals to digital signals and then again to group the data together into packets. Devices that do this translation are commonly called Analog Terminal Adapters or ATA’s.
In some cases the phone sets can be replaced by newer digital phones where the analog conversion is done in the phone itself. The conversion to digital phones has been a work in progress for some time that has seen a number of proposed transport protocols. The most common VoIP protocol at the moment is SIP (Session Initiation Protocol). I have a Cisco ATA in my house that allows me to convert all of the wireless analog phones to digital SIP phones. The ATA then registers with my home phone system (Freeswitch) which in turn registers with my ITSP.
There are a number of ITSP’s out there and I caution you to shop carefully as these guys are not subject to the availability rules of the old phone companies and can be very unreliable. I use a company out of New York called Callcentric that has very cost effective phone service and high reliability. They provide me with local 911, caller-id and many other features that I would have had to pay extra for. There is another company based in Toronto call voip.ms that has slightly better pricing and good reliability. I use them as a backup.
ITSP’s can deliver phone service to your house over an Internet connection for just a few dollars a month. Usually they have long distance plans that will allow you to dial globally for a few cents a minute and it is possible to have local numbers anywhere in the world. My wife’s family lives in Oklahoma City so I have a local number there that costs me $5 a month. If you dial that number it rings the phone in my house in Canada. It blows people’s minds when they dial a wrong number and we get one or two wrong numbers a month.
What we don’t get is telemarketers…
In my case I have a full phone system at home but my next door neighbor has his ATA register directly to the ITSP and that works just as well if not better, because there is less gear involved. Many of my neighbor’s have VoIP phone service because the local phone company was on strike when we moved into our houses. Rather than wait 6 months for a new phone line, we installed a cable based Internet service, bought an ATA and had phone service in a few days.
With cell phones as a backup (In case of power loss), VoIP is a very cost effective and flexible way to continue to have a home phone.