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.
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