I have been experimenting with FreePbx system for my friend’s company. Here is some basic background
– Number of input PSTN lines (5 - 1 Vonage, 2 Comcast VOIP, 2 teleblend)
– Number of extensions - 15
Here is a basic question I have
– I want the calling customer to always call one number (lets say 344.555.1212) whenever they want to reach anybody in the company
– One customer dials 344.555.1212 and he is connected to Sales extension (via freepbx). While this conversation is on, another customer dials 344.555.1212, HOW CAN this 2nd customer NOT GET a busy signal?
On Googling, one post seemed to imply that I need to setup the PSTN 344.555.1212 line for Call Forwarding When Busy, such that the 2nd customer (in example above) is forwarded to the 2nd PSTN number, also connected to freepbx.
The other “thought” I had, did not find a post on the web promoting or declining the following method. In this scenario, I would setup the PSTN line 344.555.1212 with simultaneous ring feature, such that it would ring multiple PSTN numbers (all connected to FreePbx). In this case, if the PSTN 334.555.1212 is busy (or not), the multple PSTN numbers will ring simulataneously and freepbx would “pick” one (or more than one … but only one would connect, the other should drop off) PSTN line. While this seems a bit complex, one major benefit here is that the only PSTN config requirement is for the 344.555.1212 number to be setup to simul-ring all the other PSTN input numbers. In comparison, in the previous (forwarding approach), each number needs to be setup for proper Call-Forwarding-When-Busy rules.
So, thoughts - I am certain I am not alone with this question. How did you solve the issue where you want to convey just one phone number to your customers, but yet allow multiple customers to dial that number simultaneously and get routed to an extension?
You could use queues or ring groups, pretty well everything is explained in the “hover over” pop up texts.
Please don’t confuse DID’s with extensions, This is a PBX and the two are well abstracted, that is what the X means. Even the extensions can be further abstracted to “follow me’s”
Twelve minutes of time spent in familiarization might well save you 120 minutes of confusion 
On the other hand it can not merge differing inbound directory numbers that you purchase from divers carriers, you will have to arrange that call forwarding with your vonage/other inbound carriers,
You need to contact your provider and ask that busy-line roll over be enabled. You will need to provide them the primary number that customers call. Once activated and a 2nd concurrent call come in, it will be sent down the 2nd phone line, etc.
On the first read, I missed the fact that you have 3 providers. You should look into each provider and see if they provide a call forward on busy option. If not, you may want to research a dedicated DID VOIP provider.
What you are describing is a “circular hunt group” . This is a common practice when using POTS trunks from the same provider. You are on the right track by suggesting the use of CFB. You’ll have to set it up manually on each incoming line. I agree with depster that the results may be problematic. I’d really look at using a dedicated SIP provider for everything. From the description you provide, it wouldn’t cost any more. Another advantage is that you will be able to utilize DIDs essentially giving everyone their own telephone number.
Thanks guys, Hmm, I thought I said both of those things already 