Dear Ankit
The success and failure of the call depends on the type of the tone/ announcement heard.
Some times the annoncement is played to handle the user behavoiur. means what user wants to hear instead of hearing a serv6er busy signal. for example a criket match is going between two countries and your team is winning so u can hear the announcement “our Team is winning” instead of server busy tone.
The call results in success only when switch tried to attempt the destination switch. and if u recieve the busy tone then its not the fault of switch so it will b considered as successful call.
for more info. contact me thru e-mail
best regards,
naveed shaikh
shaikh20@hyd.paknet.com.pk