Dialogic 6.2 Manuale Utente

ISDN Call Processing Overview

November 2009

323

The Euro-ISDN protocol only allows 20 digits to be sent as a group 

(en-block) when placing a call. For longer phone numbers, the 

application must use overlapped dialing— the process of sending 

extra digits after the initial call setup. This process allows:

„

The application to dial very large phone numbers

„

The remote end to start answering a call before it receives all the 

digits

The Bfv API automatically performs overlapped dialing on Euro-

ISDN outgoing calls using E1 or BRI lines when the phone number 

is longer than 20 digits. Users will be able to place a call with up to 

255 digits in the dial string on Euro-ISDN without requiring changes 

in the application.

Applications automatically send overlapped digits when the user 

calls BfvCallSetup, BfvLineDialString or 

BfvLineOriginateCall and provides a dial string of more than 20 

digits when Euro-ISDN is being used.

The feature divides the dial string into banks of 20 digits and uses 

the overlapped dialing feature in Euro-ISDN to send one block of 

digits at a time.

A typical module-initiated call clearing (tear down) sequence is 

illustrated in 

. The following message exchange is relative 

to the module:

1. The host initiates the call clearing procedure by sending an 

L4L3mCLEAR_REQUEST message to the module.

2. Upon receipt of the L4L3mCLEAR_REQUEST message, the 

module sends a DISCONNECT message to the network.