How diverting virtual numbers works and what is PSTN forwarding?
It’s easy to setup a virtual phone number in many different countries around the world. Dozens of service providers are now offering this feature. A virtual number, frequently called “DID number”, is not associated with a specific subscriber line. The DID can be delivered to your remote destination – most often by some form of VoIP like SIP, IAX2 or H323 – even though it originates in another country.
Typically, DIDs are landline numbers, although toll-free (freephone), cellular and premium numbers can also be virtual numbers delivered to your through VoIP.
Suppose you run a shipping line in Boston and your company maintains a large overseas base in Glasgow. Instead of having your European colleagues dial a US number each time they need to reach your headquarters, your company can setup a UK DID number (virtual number) that would ring in Boston.
UK +44 141 XXXXXXX dialed US location rings
When the UK number +441411234567 is dialed, the IP-enabled phone in the US rings, and the call is local to the calling party.
Continuing with our example, there are a number of devices that can be placed on the receiving end (Boston) to answer the call.
Some of the hardware phones (called ATAs, analogue telephone adaptors) are: Linksys (Sipura), Grandstream, Snom, Cisco Systems, Avaya, Dlink and others. These devices plug in to broadband connection and receive phone calls to DID numbers through the Internet. Most of these ATAs are SIP-based, although H323 and even IAX2 devices exist.
You will need your own IP infrastructure to register the phones to, or use some of the free SIP providers that will give you a SIP account and SIP address (URI) to receive IP calls to. Some of those providers are: Gizmo, Voipcheap, Sipgate, Callcentric, Broadvoice, FWD. You can also use their softphones (simple software for your PC or notebook) to answer calls on a computer.
DID numbers can also be forwarded to other VoIP networks. For example, DIDlogic.com provides Skype forwarding for your DID number. If you have Skype installed on your computer, you can add an incoming number (Skype also offers the same feature, called Skype-in, however, the service is not available in many countries).
China DID +86XXXXXXX dialed Your Skype software rings
Since Skype is free to use, you can also receive free calls from numbers in many countries anywhere you have Internet access – to your Skype account. DIDlogic, for example, offers DID numbers in Australia, Bulgaria, China, Iran, Israel, Latvia, Lithuania, Pakistan, Poland, Russia, South Africa, Thailand, UK and the United States.
Calls to your DID number can also be forwarded to your Google Talk, MSN, Yahoo! Messenger for free.
Israel DID +972XXXXXXX dialed Your favorite software rings
If you travel a lot, forwarding DID numbers to your VoIP software can save a lot of money. If you purchase a DID number in Australia, for example, you can receive calls from home on your Australian number anywhere you have broadband connection available (public WiFi, hotel WiFi or any other kind of hotel or visitor Internet access). As a matter of fact, you do not even need a fast Internet connection. You can run your VoIP software on a mere 80 kbit/s line and still have a high-quality conversation. That is just slightly above a good modem dialup access. It just needs to be stable. So, if you’re in, for instance, Thailand and there’s decent Internet access, you can just fire up your Google Talk or Skype and receive phone calls on your DID number at no extra cost to you.
Sometimes, however, you do not have access to your computer, or the Internet access is not working or unusable. In this case, you will need PSTN forwarding. This option can also provide significant savings if setup properly.
What is PSTN? It is an acronym for Public Switched Telephone Network. The term used to refer to analogue lines and traditional telephone systems, but in the virtual numbers context, PSTN actually means “just a normal telephone number, real phone number, another actual phone number”.
So in case of virtual numbers, divert and follow-me service, “PSTN” is just “some other line with an actual phone number”.
For example, your virtual number in China that follows you around is a DID.
You can forward it to Skype, SIP device or software, Google Talk or any other service that uses VoIP. You are forwarding your DID to an IP destination.
However, if no Internet is available, you can forward your DID to another phone number anywhere in the world – to your cellphone, for example. Or your landline number in another country. That over number is a PSTN destination.
Forwarding your virtual number in Moscow, Russia, for example, to a cellphone in the United States is PSTN forwarding:
Russian DID number +7 495XXXXXXX dialed US real cell +12135551212 rings
Forwarding to PSTN is typically not free. Some companies may charge very high per-minute rates for this service. Others will charge a certain minimum monthly fee to give you a package of minutes to various destinations in the world. Calls to European mobiles can be especially expensive since all incoming calls are free to the mobile subscribers in Europe, and the calling party pays.
Not all DID providers will let you forward your virtual number to PSTN. Those that will may charge you a lot per minute!
– $0.60/min to Swiss mobiles
– $0.35/min to Spanish mobiles
– $0.15/min to Russian mobiles
– $0.05 to landline (fixed) numbers in the US, UK and EU
Today, the rates above are very expensive. You should not pay that in 2009. This is because many virtual number providers add to the price when they buy the minutes from long-distance operators, and sell it to you at a premium. Some DID providers, however, simply give the user the same wholesale pricing as operators. This what the destinations above SHOULD ACTUALLY COST –
– $0.15/min to Swiss mobiles
– $0.09/min to Spanish mobiles
– $0.03/min to Russian mobiles
– $0.01 to landline (fixed) numbers in the US, UK and EU
DIDlogic.com provides very cheap and carrier-quality PSTN forwarding for your DID numbers.