[G1 Apps and Games] jashsu:
Making a call to a different VOIP network

So now you are able to call anyone with a SIP address or anyone in your SIP network with a number. What if you want to call someone on a different SIP network but you only have their SIP number? That's where SIPBroker comes in. Essentially, it lets you call someone on a different network using a special prefix. For example, if my number with Gizmo5 was 1-747-555-1212 and you were on Ekiga, you would find Gizmo5's prefix on SIPBroker (*747) and dial *747-1-747-555-1212 to reach me.

Now let's say you wanted to call someone on Google Talk or Yahoo/MSN Messengers. These are not SIP networks, so you could not natively communicate with them using SIP. No problem. Using the gtalk2voip service, you can voice chat with them for free.

Making a PSTN call

SIP isn't just useful for free VOIP calling. You can also call someone with a traditional phone number (a PSTN call) using VOIP and save a lot of money. The reason is because with a traditional PSTN-to-PSTN call, your carrier can control the price of the call and add a significant markup. If your VOIP service supports outbound PSTN, for the bulk of the trip your call is travelling over the internet for free. Only when it has neared its destination is it routed back into the public switched telephone network.

You ==> MobileCarrier =======================> Other Carrier ==> Friend

You --> SIP Provider ------------------------> PSTN outbound ==> Friend

=== Carrier controlled route ($$$) ---- Over the internet (cheap)

In order to make a PSTN call with Sipdroid, your SIP provider needs to support PSTN outbound. With Gizmo5, this is referred to as Call Out. Typically you will deposit a small amount of money into a prepaid account with your SIP provider and calls you make slowly draw out of this pool. The cost per minute depends only on the destination of the call. For some locations, this can mean a SIP call will be significantly cheaper than a standard PSTN call.

To make a call to a PSTN number, simply enter the number on the keypad and add a plus sign at the end, as if you were making a call to a SIP number. Your SIP provider should automatically detect it is a PSTN number and assuming it has an outbound function, route it using its PSTN outbound network. To quickly place calls to PSTN numbers using SIP from your contact list, open the contact and tap the "Text (number)" option, where (number) is the PSTN number you'd like to call using SIP. A context menu will appear letting you choose to call that number with SIP or to send a text message. Overloading the text intent is a bit of a hack, and it may change in future versions of Sipdroid.

The relationship between SIP and PSTN

Let's say you have a contact with two phone numbers, one for his PSTN number (1-510-555-1212) and one for his SIP account (1-747-123-4567).

If you tap Text 555-1212...

... and choose the Sipdroid option, you will make a SIP call and he will receive the call on his PSTN phone. You will not be able to make the call unless your SIP provider has a call out function.

... and choose the Phone option, you will make a PSTN call and he will receive the call on his PSTN phone. Your call will use up your voice minutes in accordance with your mobile carrier's voice plan. Sipdroid/SIP is not used at all in this call.
​

If you tap Text 123-4567...

... and choose the Sipdroid option, you will make a SIP call and he will receive the call on his SIP phone (or whatever he has his SIP number set up to ring). This call will not use the PSTN network at all (unless your friend has set up his SIP number to forward to the PSTN).

... and choose the Phone option, you will get an error message from your mobile carrier informing you the number is invalid or not connected.

​

Area code 800 numbers for testing outbound

If you want to test outbound calling on a SIP provider with outbound, you can call the below numbers for free. Remember to use a plus sign after the number to indicate you want to place it as a SIP call.

+18004664411 (GOOG411)

+18005558355 (Microsoft's Tell Me news service)

DID and Incoming

Recent versions of Sipdroid are now finally capable of ringing on an incoming call. However, you may be wondering, how can your friends, family and coworkers call you using SIP rather than your cellular number? The answer is using a DID number, or Direct Inward Dialling. A DID number is simply a PSTN phone number. DID numbers can be configured to forward calls to voip networks. For consumers, there are a couple of options to set up a DID for SIP. Here are a few (only discussing US DID numbers for now):

Through your SIP provider - Some SIP providers targeted toward end-users offer DID numbers as a premium service. Gizmo5 calls their DID number service "Call In".

ipkall - One of the original free DID number service. Provides a free DID number in a select number of area codes around Seattle. Only forwards to SIP.

Google Voice - This is considered by some to be the ultimate free DID service, as you can choose a number from any US area code. However, GV is much more than a DID to forward to SIP, as it is designed to completely replace all your individual contact numbers with a single number that can be programmed to forward to your other numbers. GV also offers some other services such as advanced voicemail (automatic text transcriptions, forward to email, etc) and free calling and texting to US numbers.