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oozenoz · July 7th, 2006, 10:49 AM

The digits ARE assigned to your trunks - but not within your switch. They are assigned to your trunks in the TELCO's switch.

[Telecom basics 101]

The first thing you have to understand is that the PBX you have at your location is simply a smaller version of the type of switch used by telcos in their main central offices and terminals. The same sort of digit analysis, using complex sets of tables, are used to route calls between local and long distance carriers, and to deliver calls to local premises. Whether calls are delivered over analogue lines or trunks, digital facilities with advanced features, toll free or WATS or MEGACOM, each and every call made into the PSTB is analyzed, routed, and delivered in pretty much the same way.

Let's take a call from start to finish - from a very high level. To keep it simple, let's assume you and I have the same local service provider, but we receive our local service from different central office switches because we are on the other side of the city from each other.

I pick up my POTS phone at my home and dial a number that is within your DID range. The CO switch from where I get my dial tone analyzes the number to determine where it goes - just like your PBX would do if you were dialing out. MY CO switch then routes the call according to it's rules - which say the call has to go through network trunks to YOUR CO switch.

YOUR CO switch receives the call, analyzes the digits, and determines it is within its own service area and the call needs to be delivered to your premise PBX. Nothing about the digits dialed have been changed at this point.

So, now the call is at YOUR CO switch, ready to be delivered. It knows which T1 to send it to using its internal programming - again in a similar way that your PBX knows how to route an outbound call. YOUR CO switch also knows that you are only supposed to get the last 4 digits (using Dialed Number Identification Service ) so it strips off the beginning digits and routes the call to your local premise PBX. Your PBX then acts on the call using the digits received.

July 7th, 2006, 10:49 AM	#5 (permalink)
oozenoz PBXtech PLATINUM 300+ posts Join Date: Feb 2006 Posts: 350	Re: Trunking Issue The digits ARE assigned to your trunks - but not within your switch. They are assigned to your trunks in the TELCO's switch. [Telecom basics 101] The first thing you have to understand is that the PBX you have at your location is simply a smaller version of the type of switch used by telcos in their main central offices and terminals. The same sort of digit analysis, using complex sets of tables, are used to route calls between local and long distance carriers, and to deliver calls to local premises. Whether calls are delivered over analogue lines or trunks, digital facilities with advanced features, toll free or WATS or MEGACOM, each and every call made into the PSTB is analyzed, routed, and delivered in pretty much the same way. Let's take a call from start to finish - from a very high level. To keep it simple, let's assume you and I have the same local service provider, but we receive our local service from different central office switches because we are on the other side of the city from each other. I pick up my POTS phone at my home and dial a number that is within your DID range. The CO switch from where I get my dial tone analyzes the number to determine where it goes - just like your PBX would do if you were dialing out. MY CO switch then routes the call according to it's rules - which say the call has to go through network trunks to YOUR CO switch. YOUR CO switch receives the call, analyzes the digits, and determines it is within its own service area and the call needs to be delivered to your premise PBX. Nothing about the digits dialed have been changed at this point. So, now the call is at YOUR CO switch, ready to be delivered. It knows which T1 to send it to using its internal programming - again in a similar way that your PBX knows how to route an outbound call. YOUR CO switch also knows that you are only supposed to get the last 4 digits (using Dialed Number Identification Service ) so it strips off the beginning digits and routes the call to your local premise PBX. Your PBX then acts on the call using the digits received. __________________ - calvin