1. pick up phone
if phone is out of order, let him hear that
2. Press a sequence of numbers
check with central repository
if number is present, goto step 3,
else give out error message
3. Dial this phone to the central repository of numbers
4. Establish a connection between the source and destination.
5. Give both the status message "connected"
6. While(call isnt cut)
transmit packets of voice between the two
7. If(phone is hung)
send status message to both
send the same message to central repository
8. End !
Hope mines the best answer you'll get!
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http://pcriddler.blogspot.com