Question : Voip/ISDN Terminologies

Hi All, this is an informational question, not a technical problem, but I have read a lot about this particular item and I still can not grasp the concepts (I have no telephony background), I hope someone can help me?

Can somesome explain the differences between, 1300 numbers, 1800 numbers, and ITFS numbers? What factors determine which numbers to use on a calling card platform?

Also, what is single stage dialling? At the moment, we have a platform where users dial 2#, then must enter a pin to get validated (check credit amount etc), and then dial the number they wish to call, which i believe this is considered 2 stage dialling. In my understanding, the user does not need to dial the pin, the gateway does the verification based on the number dialed from which removes the need to dial a pin. Is this correct?

Answer : Voip/ISDN Terminologies

When a customer originates a call from their phone (the A-number) to a 1300 number/1800 number (the B-number), they are actually routed (diverted/redirected) to your designated phone number (the C-number) which is not displayed to the caller.

Calls can be redirected based on the phone number being called, the location of the caller, and/or the time of day, and can be further re-directed if the destination number is busy or not answering ...
To answer the ITFS question a good post is here
http://www.webmasterworld.com/european_search_engines/3111426.htm

Definition of single stage dialing
Allows subscribers to call from their home phone number, with the prepaid service provider authenticating the call from the ANI so that their system is in the path. This prepaid service works with the subscribers home phone, without any card involved. Authentication is done without IVR behind the scenes, and is transparent to the subscriber and their users. It allows the subscriber to establish a land line account and leverage a standard POTS handset and network or SIP phone and VoIP service for international routes.

Per cisco
http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a00800e00d0.shtml#topic1
In the case of Digital Interfaces, when the PBX or central office (CO) switch sends a setup message that contains all the digits necessary to fully route the call, those digits can be mapped to an outbound Voice over IP (VoIP) dial-peer (or hairpin to plain old telephone service (POTS) dial-peer directly). The router/gateway does not present a secondary dial tone to the caller and does not collect digits. It forwards the call directly to the configured destination. This is called one stage dialing.

2 stage dialing
When a voice call comes into the Cisco IOS router/gateway, the voice port on the router is seized inbound by a PBX or CO switch. The router/gateway then presents a dial tone to the caller and collects digits until it can identify an outbound dial-peer. Whether the digits are dialed with irregular intervals by humans or in a regular fashion by telephony equipment that sends the pre-collected digits, dial-peer matching is done digit-by-digit. This means the router/gateway attempts to match a dial-peer after each digit is received. This process is called two stage dialing.