How for ANI/DID/PIN callback?
Similarly like in the calling cards scenario you can use a DID rented from a dids provider or have an own gateway connected to local telecom company. The difference is that in the callback the calls are used only for triggering the callback and therefore they never get connected, the system rejects them as soon as they come. Thus the number of required channels will be much less that in calling cards scenario when the channel stays busy by the whole duration of the call. In the callback the connection from the system to customer is realized independently, through the termination carrier defined in the dialling plan (not through the link used as an access number).
